INTRODUCTION   TO   GENERAL   SCIENCE 


THE  MACMILLAN  COMPANY 

NEW  YORK  •    BOSTON  •   CHICAGO 
SAN  FRANCISCO 

MACMILLAN  &  CO.,  LIMITED 

LONDON  •   BOMBAY  •    CALCUTTA 
MELBOURNE 

THE  MACMILLAN  CO.  OF  CANADA,  LTD. 

TORONTO 


INTRODUCTION 

TO 

GENERAL    SCIENCE 

WITH   EXPERIMENTS 


BY 

PERCY   E.    ROWELL,  B.Sc. 


Nein  g«fc 

THE   MACMILLAN   COMPANY 
1914 

AU  rights  reserved 


COPYRIGHT,  1911, 
BY  THE  MACMILLAN  COMPANY. 


Set  up  and  electrotyped.     Published  August,  1911.     Reprinted 
September,  November,  1911 ;  July,  September,  1912  ;  January, 
1913  ;  February,  1914. 


Xortoootr 

J.  S,  Cushing  Co.  —  Berwick  &  Smith  Co. 
Norwood,  Mass.,  U.S.A. 


TT.O 
MY  MOTHER 


39*771 


PREFACE 

HOWEVER  much  we  may  theorize,  and  try  to  impress  the 
youth  with  the  proper  conception  of  man's  place  in  nature, 
the  individual  young  person  will  continue  to  consider  himself 
as  the  center  of  the  universe.  Immediate  needs  and  close 
surroundings  are  what  interest  him.  It  is  not  until  he  has 
learned  about  these,  and  has  followed  back  to  their  sources 
and  causes  some  of  the  phenomena  which  have  seemed  simple 
and  matter  of  fact,  that  he  begins  to  realize  that  the  distant 
forces  have  more  effect  upon  his  existence  than  the  near-by, 
everyday  happenings.  Perhaps  it  is  well,  then,  at  the  begin- 
ning of  science  study,  to  take  his  point  of  view,  and  lead  him 
to  follow  each  apparently  simple  need  or  desire,  and  to  arouse 
in  him  the  habit  of  seeking  for  a  cause,  and  looking  beyond 
the  present  and  immediate  to  the  future  and  the  ultimate. 
It  may  be  truly  said  that  in  a  General  Science  course,  "  All 
roads  lead  to  Rome,"  for  the  course  may  be  commenced  any- 
where, and  it  will  lead  to  a  study  of  all  science.  In  fact,  if 
the  pun  may  be  forgiven,  in  a  General  Science  course,  "  All 
roads  lead  to  roam,"  and  the  pupil,  after  he  is  started,  needs 
but  to  be  guided.  That  is  the  purpose  of  this  book. 

It  is  not  easy  to  teach  a  course  in  general  science  success- 
fully. There  is  always  the  temptation  to  specialize  in  some 
particular  part,  usually  the  part  which  the  teacher  likes  best, 
and  about  which  he  knows  most.  If  this  temptation  is  not 
resisted,  the  course  ceases  to  be  general. 

The  value  of  a  General  Science  course  is  twofold.  Know- 
ing a  little  about  a  great  many  sciences  enables  the  pupil  to 

vii 


Vlll  PREFACE 

obtain  a  bird's-eye  view  of  all,  and  a  day's  lesson  in  some  one 
of  the  elementary  sciences  ceases  to  be  a  blind  alley,  or  a  path 
which  must  be  followed  with  complete  faith  that  the  teacher 
knows  where  it  will  lead.  The  pupil  can  see  the  interrelation 
of  all  sciences,  and  can  reason  from  many  points  of  view. 
The  other  value  lies  in  awakening  the  mind  to  the  vast  pos- 
sibilities of  scientific  knowledge  and  mental  attainments.  A 
course  in  general  science  should  reach  every  pupil  in  at  least 
one  science  and  stimulate  his  ambition  to  learn  more  of  it. 
If  this  be  true,  we  must  have  two  purposes  in  the  presenta- 
tion of  such  a  course,  —  to  overcome  narrowness,  and  to 
stimulate  ambition. 

-  If  there  is  not  a  definite  plan  for  the  year's  work,  a  goal 
toward  which  the  class  is  to  strive,  there  must  be  waste  of 
time  and  loss  of  interest.  This  book  is  offered  in  the  hope 
that  it  may  aid  and  guide  the  teacher,  as  well  as  help  the 
pupils,  always  allowing  for  initiative  on  the  part  of  both. 
Such  a  course  is  elastic  and  can  never  be  limited  by  an  outline, 
however  full.  While  a  large  proportion  of  the  experiments 
are  standard,  it  has  been  the  author's  endeavor  to  require 
simple  apparatus  and  chiefly  qualitative  work.  Several  of 
the  experiments  are  believed  to  be  new,  and  the  element  of 
play  has  been  brought  in  wherever  it  seemed  feasible.  The 
numbering  of  the  reference  books  is  arbitrary,  but  must 
necessarily  be  so,  as  the  Dewey  system  is  not  sufficiently 
graduated  for  exact  reference.  Local  conditions  should  by 
all  means  be  emphasized,  for,  to  be  valuable,  the  course  must 
touch  the  lives  of  the  pupils  in  as  many  places  as  possible. 

The  book  may  be  used  without  any  of  the  reference  books 
except  the  publications  of  the  United  States  government. 
However,  the  references  have  been  divided  into  two  groups: 
one  contains  fourteen  books  for  general  supplementary  work; 


PREFACE  IX 

the  other  comprises  seventy-six  books,  so  chosen  as  to  enable 
the  instructor  to  emphasize  any  particular  branch  of  science. 
It  is  not  intended  that  all  of  the  references  be  utilized.  The 
General  Science  course  should  be  adapted  to  the  locality.  It 
is  easier  for  the  teacher  to  select  what  is  wanted,  from  a  suffi- 
ciently large  list,  than  it  is  to  hunt  for  material  outside  of  the 
references. 

In  addition  to  these  library  books,  the  list  of  the  publica- 
tions of  the  United  States  Department  of  Agriculture  is  quite 
large  and  the  number  of  references  to  them  considerable. 
New  publications  are  constantly  appearing,  and  the  teacher 
may  add  to  this  list  indefinitely.  The  pupils  should  be  urged 
to  get  the  "  bulletin  habit." 

I  wish  to  thank  the  publishers  of  the  books  to  which  I  have 
referred  for  their  kindness  and  cooperation,  and  the  teachers 
who  have  supplied  me  with  valuable  suggestions.  Especially 
do  I  wish  to  express  my  appreciation  to  Mr.  Allan  B.  Camp- 
bell for  his  assistance,  without  which  the  appearance  of  the 
book  this  year  would  have  been  impossible.  To  one  other, 
however,  the  greatest  credit  is  due,  for  her  assistance  ex- 
tends back  through  many  patient  years,  and  without  her 
stimulating  influence  the  ability  to  gather  together  the  facts 
contained  in  this  outline  would  have  been  an  impossibility  at 
any  time.  To  her  this  book  is  dedicated. 

PERCY  ELLIOTT  ROWELL. 

Los  ANGELES,  CALIFORNIA, 
July,  1911. 


CONTENTS 

M?CTION                      •  PAGK 

1.  Explosions       ..........  1 

2.  Composition  of  Matter — Definition  of  Heat          ...  2 

3.  States  of  Matter 3 

4.  Combustion 5 

•    5.   Oxygen  —  Its  Uses  and  Action 8 

6.  Fuels 10 

7.  Blasting 11 

8.  Gas  and  Gasoline  Engines      .......  11 

9.  Animal  Heat 12 

10.  Flames 14 

11.  First  Aid  to  the  Burnt 15 

12.  Sterilization  by  Heat 16 

13.  Antiseptic  Washes  —  Disinfectants 17 

14.  Chemical  Effects  of  Heat        .  * 19 

15.  Expansion  Due  to  Heat 19 

16.  Temperature  and  its  Measurement         .....  21 

17.  Conduction 23 

18.  Convection       .         .        . 24 

19.  Ventilation  and  Heating  of  Buildings 26 

20.  Radiation  of  Heat 27 

21.  Absorption  of  Heat 28 

22.  Measurement  of  Heat      .         .        .        .   •     .        .        .        .30 

23.  Heat  of  Change  of  State 31 

24.  Evaporation  Requires. Heat    .......  34 

25.  Applications  of  Evaporation  and  Condensation     ...  35 

26.  The  Steam  Engine 38 

27.  Distillation  of  Liquids 38 

28.  Destructive  Distillation 40 

29.  Cooking 42 

30.  Chemical  and  Physical  Changes 44 

31.  Chemical  Combination  Produces  Heat 46 

32.  Friction  and  Compression  Produce  Heat        .        .        .         .47 

xi 


xii  CONTENTS 


33.  Radium  Produces  Heat  ........  49 

34.  The  Sun  ...........  50 

35.  The  Sun  the  Source  of  All  Energy         .....  51 

36.  Theories  ...........  52 

37.  The  Laws  of  Motion       ........  53 

38.  Effects  of  Two  or  More  Forces  Acting  at  the  Same  Time     .  55 

39.  Universal  Gravitation     ........  56 

40.  The  Center  of  Gravity    ........  57 

41.  The  Effect  of  Two  Forces  Acting  at  Right  Angles  to  Each 

Other  .         .        .........  58 

42.  The  Measurement  of  Rotary  Motion      .....  59 

43.  Theories  of  the  Evolution  of  the  Solar  System      ...  61 

44.  The  Solar  System    .........  63 

45.  The  Planets  and  the  Earth     .......  63 

46.  Age  of  the  Earth     .....        „./;.'.  65 

47.  The  Shape  and  Size  of  the  Earth  .        .        ,                 .        .  65 

48.  The  Heat  of  the  Earth   .         ....',        .        .  67 

49.  Direction  —  Latitude  and  Longitude      .      .  .        .        .        .  68 

50.  Motions  of  the  Earth      .         .......  69 

51.  Time       ..       .        .        .        .        .        .        .        .        .        .  71 

52.  The  Seasons     .        .'    -   ,  -'     .        .  >      .        .        .        .<.      .  72 

53.  The  Calendar  .......     '    ...  74 

54.  The  Moon        .        .        .        ...       .        .        ....  75 

55.  Tides        .        .        «        .                 .,  \   .        .        .        .    •     .  76 

56.  Meteors   .        .        .        .        .        .      ,  .        ;        .        .        .  77 

57.  Comets    .         ;      .  .........  78 

58.  The  Stars         ......        .        .        .        .79 

59.  Distances  of  the  Stars     ......        .        .80 

60.  The  Earth  as  a  Whole    ........  80 

61.  The  Earth  as  a  Magnet  ......        ...  81 

62.  Other  Magnets    '     ......        .        .         .83 

63.  The  Northern  Lights      .        .        .        .        .        ...         .85 

64.  Sources  of  P^lectricity      ........  86 

65.  Applications  of  Electricity      .     '  ."       .        .       ••,'•*        •  88 

66.  Chemical  Effects  of  Electricity       .        .        .        .        »        .  90 

67.  Heat  and  Light  from  Electricity     ....        .       ...       .  91 

68.  Heat  Produces  Light       .        .        .        ,-        .        .        .        .  94 

69.  Light  and  Vision    ....        »,.  •    .        *        .        .  95 

70.  Reflection                                                                            .        .  96 


CONTENTS  Xlll 


71.  Color 98 

72.  Refraction  and  Dispersion 100 

73.  The  Rainbow 101 

74.  Diffusion  of  Light 102 

75.  Twilight 103 

76.  Transmission  of  Light  — Shadows 104 

77.  Eclipses          .  104 

78.  Measurement  of  Light 105 

79.  Photography 107 

80.  The  Atmosphere  and  its  Composition 109 

81.  Weight  of  the  Air .110 

82.  Atmospheric  Pressure  and  the  Barometer    .         .        .        .112 

83.  Boiling  from  Another  Point  of  View 114 

84.  "Suction" 115 

85.  Pumps '  .        .116 

86.  The  Siphon 117 

87.  Nitrogen  and  its  Uses   ........     118 

88.  Effects  of  Painting  —  Wood  Preservation    .         .        .         .120 

89.  Carbon  Dioxide     .         .         . 122 

90.  The  Chemical  Engine 124 

91.  Other  Constituents  of  the  Atmosphere          ....     125 

92.  Atmospheric  Electricity 126 

93.  Warming  the  Air 127 

94.  Winds 128 

95.  Kinds  of  Winds     .         .        . 129 

96.  Velocity  of  Winds         .        . 130 

97.  Resolution  of  Forces      .        .        .        •        •        •        •        .131 

98.  The  Theory  of  the  Kite         .        .        .        .        .        .        .133 

99.  The  Theory  of  the  Aeroplane       .        ...        .        .        .135 

100.  Sailing  a  Boat 137 

101.  Humidity 138 

102.  Dew        ". 139 

103.  Frost 141 

104.  Fog  and  Clouds 142 

105.  Snow  and  Hail 143 

106.  Rainfall  — Cyclones 144 

107.  Weather  Observations 146 

108.  Weather  and  Climate 148 

109.  Weather  Instruments    .  ......     149 


Xiv  CONTENTS 

SECTION  PAGE 

110.  Home-made  Weather  Instruments 150 

111.  The  Ocean 150 

112.  Purification  of  Water 152 

113.  Springs  and  Streams 155 

114.  Composition  of  Water 156 

115.  Solution  and  its  Effects 157 

116.  Uses  of  Water        .                                   160 

117.  Surface  Tension 162 

118.  Capillarity 164 

119.  Osmosis 166 

120.  Removal  of  Grease  Spots  and  Stains    .....  168 

121.  Acids,  Bases,  and  Salts  —  Neutralization     ....  170 

122.  Hygroscopic  and  Efflorescent  Salts 173 

123.  Soap 174 

124.  Hard  Water 176 

125.  The  Earth's  Crust 177 

126.  Changes  in  the  Surface  of  the  Earth    .        .        .         .         .178 

127.  Weathering  and  the  Rate  of  Weathering     .         .        .         .179 

128.  Agents  of  Weathering .  180 

129.  Erosion 182 

130.  Agents  of  Erosion 183 

131.  Disintegration  Due  to  Plant  and  Animal  Life  —  Bacteria  .  184 

132.  Slowness  of  Change       .        . 185 

133.  Rocks  Defined  and  Classified 186 

134.  The  Difference  between  Minerals  and  Rocks       .         .         .187 

135.  Rocks  of  the  Earth's  Crust 188 

136.  Organic  Rocks 191 

137.  Coal,  Soft  and  Hard      .         .         .        .        •        »/,-..      •  192 

138.  Petroleum  and  Natural  Gas  .        .        .        .        .*      .        •  194 

139.  How  Mountains  are  Made     .        .        .  '.'    *, '      •                 •  .195 

140.  The  Source  of  Food  —  The  Soil   .        .        .        .        •        .196 

141.  The  Farm  a  Workshop         .        .        ,..      .        -        .        .  197 

142.  Resources  of  the  Soil 199 

143.  Kinds  of  Soil 20° 

144.  Transportation  of  Soils 2°1 

145.  Texture  of  the  Soil 202 

146.  Importance  of  Moisture 204 

147.  How  Water  is  Held  in  the  Soil 205 

148.  To  Increase  the  Moisture-holding  Capacity  — Tilling          .  206 


CONTENTS  XV 


149.  Conservation  of  Moisture  —  Tilling      •        .        .        .        .  207 

150.  Irrigation  and  Underdrainage       ......  210 

151.  Soil  Air 212 

Plant  Food  — I 213 

Humus .        .        .        .215 

Enriching  the  Soil .        .216 

Green  Manures      .        .        .        .        .        .        .        .         .  217 

Barnyard  Manure          .         .        .         .        .        .        .         .218 

Renovation  of  Worn-out  Soils 220 

The  Liming  of  the  Soil '   .        .220 

Commercial  Fertilizers 222 

Use  of  Commercial  Fertilizers 223 

Home-mixed  Fertilizers 224 

Fertilizers  for  Garden  Crops 225 

Plant  Roots 226 

Plant  Stems 227 

Leaves 228 

Buds      .        . 230 

Flowers          . 231 

Fruits  and  Seeds   .         .         . 232 

Flavoring  Extracts  and  Perfumes 234 

Plant  Food— II 235 

171.  The  Propagation  and  Breeding  of  Plants     .         .         .         .236 

172.  Plants  — Forestry 237 

173.  Lower  Forms  of  Plant  Life  —  Bacteria,  Molds,  and  Mildew  238 

174.  Fermentation  —  Yeasts 240 

175.  Alcohol  for  Purposes  of  Energy 241 

176.  Lower  Forms  of  Plant  Life  —  Fungi,  Rusts,  Mushrooms, 

etc. 243 

177.  Protozoa  and  Amoebae 244 

178.  Insects  and  the  Smaller  Animals           .         .         ...         .  245 

179.  The  Stings  of  Insects    .        .         .     * 246 

180.  Animal  Life  —  Distribution 247 

The  Invertebrates .        .247 

Animal  Life  —  Fishes,  Animals,  and  Birds  .        .         .        .  248 

Animal  Life  —  Man 249 

The  Life  Processes 250 

The  Bones,  or  Framework 251 

The  Lever  and  its  Advantage 252 


XVi  CONTENTS 

SECTION  PAGE 

187.  The  Muscles 254 

188.  The  Blood 255 

189.  Respiration 255 

190.  Dangers  of  Vitiated  Air 257 

191.  Food  and  Nutrition 259 

192.  Digestion       .' 260 

193.  Food  — Vegetable  Food 262 

194.  Food  — Animal  Food 263 

195.  Food  Analysis 264 

196.  Water  Analysis     .         .         . 268 

197.  Food  — Preservation  of  Food 270 

198.  The  Mind .         .271 

199.  The  Senses  — Sight 272 

200.  Sound  and  Hearing .  274 

201.  Man's  Place  in  Nature 277 

202.  Nature  and  Business 278 

203.  Man's  Applications  of  Nature's  Principles  ....  279 

204.  How  to  Plan  a  House  and  Barn 280 

205.  Conveniences  for  the  Home 282 

206.  Sanitation 284 

207.  Sanitary  Plumbing 285 

208.  Simple  Household  Remedies 287 

209.  Reading  Meters     . 290 

210.  Economy        .         .         .        . 291 

211.  Education  and  Civilization 293 

212.  Manner  of  Living .  294 


LIST   OF  EXPERIMENTS 

•   SECTION  PAGE 

1.  Experiments  for  the  Teacher 1 

2.  Experiments  for  the  Teacher  (in  reference  book  1803)          .  3 

4.  Expt.    1.     Ordinary  Combustion 5 

Expt.    2.     Spontaneous  Combustion 6 

5.  Expt.    3.     Oxygen  and  Combustion 8 

9.   Expt.    4.     Complete  and  Incomplete  Combustion         .        .  13 

10.   Expt.    5.     Source  of  Flames 15 

15.  Expt.    6.     Expansion  Due  to  Heat 20 

16.  Expt.    7.     The  Fixed  Points  of  the  Thermometer        .         .  22 

17.  Expt.    8.     Conduction 23 

18.  Expt.    9.     Convection  in  Gases      ......  25 

Expt.  10.     Convection  in  Water 25 

20.  Expt.  11.     Radiation  of  Heat 28 

21.  Expt.  12.     Absorption  of  Heat 30 

22.  Expt.  13.     Quantity  of  Heat  Comparison      ....  31 

23.  Expt.  14.     Heat  of  Change  of  State 33 

25.   Expt.  15.     Cooling  by  Evaporation 37 

Expt.  16.     Heating  by  Condensation 37 

27.  Expt.  17.     Distillation 39 

28.  Expt.  18.     Destructive  Distillation 41 

29.  Experiment  for  the  Home       .         .         .  •       .         .        .         .44 

30.  Expt.  19.     Physical  and  Chemical  Changes  .         .        .        .45 

31.  Experiments  for  the  Teacher 47 

32.  Experiments  for  the  Home 48 

Experiment  for  the  Teacher 49 

37.  Expt.  20.     Inertia  and  Reaction 54 

38.  Experiment  for  the  Teacher 55 

40.  Expt.  21.   Center  of  Gravity  .         .        .        .        .        .         .58 

41.  Experiment  for  the  Home 59 

Ar'.   Expt.  22.     To  Make  and  Use  a  Clinometer   ....  60 

49.    Expt.  23.     To  Locate  the  North  by  Means  of  the  Sun  .         .  69 

Expt.  24.     To  Locate  the  South  by  Means  of  a  Watch          .  09 


XVlll  LIST  OF  EXPERIMENTS 

SECTION  PAGE 

52.  Expt.  25.  The  Seasons  —  Length  of  Day  and  Night .        .      73 

61.  Expt.  26.     The  Earth's  Magnetism 82 

62.  Expt.  27.     Magnetism 84 

64.  Expt.  28.     Sources  of  Electricity 87 

65.  Expt.  29.  The  Electric  Bell,  Telegraph,  and  Telephone     .       90 

66.  Expt.  30.     Electroplating 91 

Expt.  31.     The  Storage  Cell 92 

67.  Expt.  32.  Heat  and  Light  from  Electricity        ...       93 

68.  Expt.  33.     Heat  Produces  Light 95 

70.  Expt.  34.     Reflection 97 

71.  Expt.  35.     Color 99 

72.  Expt.  36.     Refraction  and  Dispersion 101 

73.  Expt.  37.     The  Rainbow 102 

78.  Expt.  38.  Candle  Power  —  The  Photometer       .         .         .106 

79.  Expt.  39.  Effect  of  Light  upon  a  Silver  Salt      .         .         .108 

80.  Expt.  40.     Composition  of  Air 110 

81.  Expt.  41.     Weight  of  Air     . Ill 

82.  Expt.  42.     Atmospheric  Pressure 113 

83.  Expt.  43.  Boiling  at  Reduced  Pressure       .         .        .        .115 

84.  Expt.  44.     "Suction" 116 

86.  Expt.  45.     The  Siphon 118 

87.  Expt.  46.     To  Prepare  Nitrogen 119 

88.  Expt.  47.     The  Testing  of  Paint 121 

89.  Expt.  48.  Sources  of  Carbon  Dioxide          .         .         .         .123 

90.  Expt.  49.  Preparation  of  Carbon  Dioxide  —  The  Chemi- 

cal Engine          .........     125 

97.  Expt.  50.     Resolution  of  Forces 132 

98.  Expt.  51.     To  Make  a  Malay  Kite 134 

99.  Expt.  52.     To  Make  a  Boomerang 136 

100.  Expt.  53.     To  Make  a  Windmill 138 

101.  Experiment  for  the  Teacher 139 

102.  Expt.  54.  The  Dew  Point  .  .        .        .        .        .141 

105.  Expt.  55.     Sublimation 144 

107.  Expt.  56.     Temperature  Curves 147 

110.  Experiments  for  the  Home 150 

112.  Exrjt.  57.  Precipitation  and  Filtration        .        .         .         .153 

114.  Expt.  58.     To  Prepare  Hydrogen 157 

Experiment  for  the  Teacher          .         .         .         .         .         .157 

115.  Expt.  59.     Solution  and  its  Effects 159 


LIST  OF  EXPERIMENTS  xix 


SECTION 

116.   Expt.  60. 
117.   Expt.  61: 
118.   Expt.  62. 
119.   Expt.  63. 
120.   Expt.  64. 
121.   Expt.  65. 
122.   Expt.  66. 
123.   Expt.  67. 
124.   Expt.  68. 
135.   Expt.  69. 
136.   Expt.  70. 
138.   Expt.  71. 
145.    Expt.  72. 
149.   Expt.  73. 
151.   Experimei 
Expt.  74. 
158.   Expt.  75. 
163.   Expt.  76. 
164.   Expt.  77. 
165.   Expt.  78. 
168.   Expt.  79. 
169.   Expt.  80. 
175.   Expt.  81. 
186.    Expt.  82. 
190.   Expt.  83. 
192.   Expt.  84. 
193.   Expt.  85. 
195.   Expt.  86. 
Expt.  87. 
196.   Expt.  88. 
199.   Expt.  89. 
200.    Expt.  90. 
Expt.  91. 
209.   Experimer 
210.   Expt.  92. 

Specific  Gravity  —  Bouyancy      .... 
Surface  Tension  
Capillarity  
Osmotic  Pressure         

PAGE 

161 
163 
165 
167 
169 
172 
174 
175 
177 
190 
192 
195 
203 
209 
213 
213 
221 
227 
228 
229 
233 
234 
243 
253 
258 
261 
263 
265 
267 
269 
273 
275 
275 
291 
293 

Acids,  Bases,  and  Salt  —  Neutralization     . 
Efflorescence  and  Deliquescence 
To  Make  Soap     
Temporary  Hardness  
Sedimentation     
To  Test  Rocks    

The  Effect  of  Mulches        ..... 

it  for  the  Teacher         
Air  Necessary  for  Roots     
The  Effect  of  Lime—  Acid  Soils 

The  Pressure  of  Sap   ...         ... 
Transpiration      
Seed  Testing  —  Germination      .... 

Sources  of  Alcohol      .        . 
The  Lever   
Test  for  Bad  Air         

The  Amount  of  Water  in  Vegetables 
Composition  of  Food  
Test  for  Food  Preservatives  and  Colors 
Water  Analysis  ....... 
Persistence  of  Vision  —  Fatigue         .         ... 
The  Origin  of  Sound  —  Music    . 
The  Megaphone  and  the  Mechanical  Telephone 
its  for  the  Home  '.        . 

EXPLANATION  OF  BOOK  NUMBERING 

THE  numbers,  as  given  in  the  list  which  follows,  may  be 
written  on  Dennison's  Labels  No.  539,  and  affixed  to  the  back 
of  the  binding,  below  the  title  of  the  respective  books.  This 
must  be  in  addition  to  any  other  system  of  numbering,  and  it 
may  be  well  to  number  the  books  also  on  the  inside  of  the  front 
cover,  in  order  to  save  time  in  case  the  outside  labels  come 
off. 

It  would  be  advisable  to  segregate  the  books  to  be  used 
with  this  outline,  and  to  arrange  them  according  to  the  num- 
bering. This  plan  permits  the  pupils  to  work  rapidly  and 
effectively,  since  they  may  obtain  a  desired  book,  directly  by 
number,  without  hunting  for  title  or  author.  Wherever  this 
system  has  been  established,  success  has  marked  it  from  the 
start.  The  starred  books  are  those  which  are  referred  to  by 
number,  and  are  the  most  important  in  connection  with  this 
outline. 

The  publications  of  the  United  States  Department  of  Ag- 
riculture may  be  obtained,  free  of  charge,  by  addressing  the 
Secretary  of  Agriculture,  Washington,  D.  C.  A  catalogue  of 
the  publications  of  this  department  will  serve  as  a  source  of 
valuable  information,  and  it  should  be  in  the  hands  of  every 
science  teacher.  It  may  be  obtained  free  upon  application. 
The  teacher  should  have  the  school  listed  to  receive  the 
"  Monthly  List  of  Publications,"  which  is  sent  free  upon  re- 
quest. 

xxi 


XX11 


EXPLANATION  OP  SOOK  NUMBERING 


If  the  teacher  desires  to  add  books  to  this  list,  the  next 
higher  number  may  be  used,  in  the  proper  classification,  and 
references  made  at  the  proper  places  in  the  text.  Thus  the 
book  may  be  adapted  to  any  locality,  and  may  be  used  to 
guide  the  thoughts  of  the  pupils  in  any  desired  direction. 


1001. 
*1002. 

1003. 

1004. 

1005. 

1006. 

1007. 

1008. 

1009. 

1010. 

1101. 

1102. 
*1103. 

1104. 

1105. 

1106. 

1107. 

1108. 

1109. 

1110. 

1201. 

1202. 

1203. 

1204. 
*1205. 

1206. 

1207. 

1208. 

1209. 

1210. 


NUMBERING  FOR  REFERENCE  BOOKS 

Elements  of  Astronomy.     Young.     Ginn. 
Introduction  to  Astronomy.     Moulton.     Macmillan. 
Elements  of  Astronomy.     Newcomb.     A.  B.  Co. 
Lessons  in  Astronomy.     Young.     Ginn. 


Exercises  in  Meteorology. 
Elementary  Meteorology. 
Elementary  Meteorology. 


Ward.     Macmillan. 
Davis.     Ginn. 
Waldo.    A.  B.  Co. 


Rocks  and  Minerals.     Fairbanks.     Educ.  Pub.  Co. 
Rocks — Weathering  and  Soils.     Merrill.     Macmillan. 
The  Earth  and  Its  Story.     Heilprin.     Silver,  Burdett. 
Story  of  Our  Continent.     Shaler.     Ginn. 
Elements  of  Geology.     Norton.     Ginn. 
Elementary  Geology.     Tarr.     Macmillan. 
Outlines  of  the  Earth's  History.     Shaler.     Appleton. 
Common  Rocks  and  Minerals.     Crosby.     Heath. 
Textbook  of  Geology.     Brigham.     Appleton. 
Compend  of  Geology.     Le  Conte.     A.  B.  Co. 


EXPLANATION   OF  BOOK  NUMBERING          XX1U 

1211. 
1212. 
1213. 
1214. 
1215. 

1301.  First  Book  of  Physical  Geography.     Tarr.     Macmillan. 

1302.  Lessons  in  Physical  Geography.     Dryer.     A.  B.  Co. 

1303.  Elementary  Physical  Geography.     Davis.     Ginn. 
*1304.  New  Physical  Geography.     Tarr.     Macmillan. 

1305.  Eclectic  Physical  Geography.     Hinman.     A.  B.  Co. 

1306.  Elementary  Physical  Geography.     Tarr.     Macmillan. 

1307.  Elementary  Physical  Geography.     Redway.     Scribners. 

1308.  Physical  and  Commercial  Geography.    Gregory,  Keller,  Bishop. 

Ginn. 

1309.  Physical  Geography.     Maury-Simonds.     A.  B.  Co. 

1310.  Physical  Geography.     Salisbury.     Holt. 

1311.  Introduction  to  Physical  Geography.     Gilbert,  Brigham.     Ap. 

pleton. 

1312.  Elements  of  Physical  Geography.     Hopkins.     Sanborn. 

1313.  A  Reader  in  Physical  Geography.     Dodge.     Longmans. 
1314. 

1315. 

1401.  The  Foundations  of  Botany.     Bergen.     Ginn. 

1402.  Botany.     Bailey.     Macmillan. 

1403.  First  Lessons  with  Plants.     Bailey.     Macmillan. 

1404.  Experiments  with  Plants.     Osterhout.     Macmillan. 

1405.  Elements  of  Botany.     Bergen.     Ginn. 

1406.  Botany  All  the  Year.     Andrews.     A.  B.  Co. 
*1407.  Principles  of  Botany.     Bergen-Davis.     Ginn. 

1408. 

1409. 

1410. 

*1501.  Applied  Physiology.     Overton.     A.  B.  Co. 

1502.  Nature  Study  and  Life.     Hodge.     Ginn. 

*1503.  Elements  of  Biology.     Hunter.     A.  B.  Co. 

1504.  Elementary  Biology.     Parker.     Macmillan. 

1505.  First  Course  in  Biology.     Bailey,  Coleman*.     Macmillan. 

1506.  Human  Body  and  Health.     Davison.     A.  B.  Co. 

1507.  Advanced  Physiology  and  Hygiene.      Conn  and  Budington. 

Silver,  Burdett. 


xxiv  EXPLANATION  OF  BOOK  NUMBERING 

1508.  Animal  Activities.     French.     Longmans. 

1509.  Principles  of  Physiology  and  Hygiene.     Fitz.     Holt. 

1510.  Physiology  of  Man.     Moore.     Holt. 

1511.  Academic  Physiology  and  Hygiene.     Brands.     Sanborn. 

1512.  Zoology,  Descriptive  and!  Practical.     Colton.     Heath. 
1513. 

1514. 
1515. 

*1601.  The  Soil.     King.     Macmillan. 

1602.  First  Principles  of  Agriculture.     Goff  and  Mayne.     A.  B.  Co. 

1603.  Agriculture  for  Beginners.     Burkett,  Stevens,  Hill.     Ginn. 

1604.  The  Great  World  Farm.     Gaye.     Macmillan. 
*1605.  Elements  of  Agriculture.     Warren.     Macmillan. 

1606.  Principles  of  Agriculture.     Bailey.     Macmillan. 

1607.  Physics  of  Agriculture.     King.     King. 

1608.  Practical  Agriculture.     Wilkinson.     A.  B.  Co. 

1609.  How  Crops  Grow.     Johnson.     Judd. 

1610.  First  Principles  of  Agriculture.     Voorhies.     Silver,  Burdett. 

1611.  Agriculture,  Pacific  Slope.      Hilgard  and  Osterhout.      Mac- 

millan. 

1612.  Soils.     Burkett.     Orange  Judd. 
1613. 

1614. 

1615. 

1701.  Elementary  Study  of  Chemistry.     McPherson  and  Henderson. 

Ginn. 

*1702.  Chemistry  of  Plant  and  Animal  Life.     Snyder.     Macmillan. 

*1703.  Essentials  of  Chemistry.     Hessler  and  Smith.     Sanborn. 

1704.  Manual  of  Chemistry.     Storer  and  Lindsay.     A.  B.  Co. 

1705.  Elementary  Experimental  Chemistry.     Ekeley.     Silver,  Bur- 

dett. 

1706.  Descriptive  Chemistry.     Newell.     Heath. 

1707.  Chemistry  (briefer).     Remsen.     Holt. 

1708.  Essentials  of  Chemistry.     Williams.     Ginn. 

1709.  First  Principles  of  Chemistry.     Brownlee,  etc.     Allyn  &  Bacon. 
*1710.  Sanitary  and  Applied  Chemistry.     Bailey.     Macmillan. 

1711.  Elementary  Chemistry.     Bradley.     Appleton. 

1712.  Elementary  Chemistry.     Godfrey.     Longmans. 

1713.  History  of  Chemistry.     Venable.     Heath. 
1714. 


EXPLANATION  OF  BOOK  NUMBERING  xxv 

1715. 

1801.  High  School  Physics.     Carhart  and  Chute.     Allyn  &  Bacon. 

1802.  Forty  Lessons  in  Physics.     McMullen.     Holt. 
*1803.  First  Course  in  Physics.     Millikan  and  Gale.     Ginn. 

1804.  Principles  of  Physics.     Gage.     Ginn. 

1805.  Physics  for  Secondary  Schools.     Adams.     A.  B.  Co. 

1806.  A  Textbook  of  Physics.     Hall  and  Bergen.     Holt. 

1807.  Elements  of  Physics.     Coleman.     Heath. 

1808.  A  Brief  Course  in  Physics.     Hoadley.     A.  B.  Co. 

1809.  Textbook  of  Physics.     Linebarger.     Heath. 

1810.  Elements  of  Physics.     Sanford.     Holt. 

1811.  Elementary  Physics.     Miller  and  Foerste.     Scribners. 
1812. 

1813. 
1814. 
1815. 
*1901.   Bacteria,  Yeasts,  and  Molds.     Conn.     Ginn. 

1902.  Agricultural  Bacteriology.     Conn.     Blakiston. 

1903.  Bacteria  in  Relation  to  Country  Life.     Bailey.     Macmillan. 

1904.  Primer  of  Sanitation.     Ritchie.     World. 

1905.  School    Sanitation    and    Decoration.      Burrage    and   Bailey. 

Heath. 
1906. 
1907. 
1908. 
1909. 
1910. 


PUBLICATIONS   OF   THE  UNITED   STATES   DEPARTMENT 
OF  AGRICULTURE  ^ 

FARMERS'   BULLETINS 

No.  28.  Weeds  and  How  to  Kill  Them. 

No.  34.  Meats ;  Composition  and  Cooking. 

No.  44.  Commercial  Fertilizers. 

No.  54.  Some  Common  Birds. 

No.  77.  The  Liming  of  Soils. 

No.  78.  Experiment  Station  Work  ;  Miscellaneous. 

No.  79.  Experiment  Station  Work ;  Miscellaneous. 


XX  vi  PUBLICATIONS 

No.    85.   Fish  as  Food. 

No.    86.   Thirty  Poisonous  Plants. 

No.    93.   Sugar  as  Food. 

No.  104.   Notes  on  Frost. 

No.  105.   Experiment  Station  Work ;  Miscellaneous. 

No.  121.   Beans,  Peas,  and  Other  Legumes  as  Food. 

No.  122.    Experiment  Station  Work ;  Miscellaneous. 

No.  126.   Practical  Suggestions  for  Farm  Buildings. 

No.  127.   Important  Insecticides. 

No.  128.   Eggs  and  their  Uses  as  Food. 

No.  131.   Household  Tests  of  Butter. 

No.  134.   Tree  Planting  on  Rural  School  Grounds. 

No.  138.   Irrigation  in  Field  and  Garden. 

No.  142.   Principles  of  Nutrition  and  Nutritive  Value  of  Food. 

No.  145.    Carbon  Bisulphid  as  an  Insecticide. 

No.  155.   How  Insects  Affect  Health  in  Rural  Districts. 

No.  157.   The  Propagation  of  Plants. 

No.  162.   Experiment  Station  Work ;  Miscellaneous. 

No.  173.   Primer  of  Forestry.     Part  I.  The  Forest. 

No.  175.   Home  Manufacture  and  Use  of  Unfermented  Grape  Juice. 

No.  181.   Pruning. 

No.  182.   Poultry  as  Food. 

No.  183.   Meat  on  the  Farm ;  Butchering,  Curing,  etc. 

No.  185.   Beautifying  the  Home  Grounds. 

No.  187.   Drainage  of  Farm  Land. 

No.  188.   Weeds  Used  in  Medicine. 

No.  192.   Barnyard  Manure. 

No.  196.   Usefulness  of  the  American  Toad. 

No.  203.   Canned  Fruits,  Preserves,  and  Jellies. 

No.  204.   The  Cultivation  of  Mushrooms. 

No.  222.   Experiment  Station  Work ;  Miscellaneous. 

No.  228.    Forest  Planting  and  Farm  Management. 

No.  243.    Fungicides. 

No.  245.   Renovation  of  Worn-out  Soil. 

No.  249.   Cereal  Breakfast  Foods. 

No.  255.   The  Home  Vegetable  Garden. 

No.  256.   Preparation  of  Vegetables  for  the  Table. 

No.  259.    Experiment  Station  Work ;  Miscellaneous. 

No.  263.    Practical  Information  in  Irrigation. 

No.  266.   Management  of  Soils  to  Conserve  Moisture. 


PUBLICATIONS  xxvii 

No.  270.  Modern  Conveniences  for  the  Farm  Home. 

No.  277.  The  Use  of  Alcohol  and  Gasoline  in  Farm  Engines. 

No.  278.  Leguminous  Crops  for  Green  Manuring. 

No.  293.  Use  of  Fruit  as  Food. 

No.  295.  Potatoes  and  Other  Root  Crops  as  Food. 

No.  298.  Food  Value  of  Corn  and  Corn  Products. 

No.  305.  Experiment  Station  Work ;  Miscellaneous. 

No.  317.  Experiment  Station  Work ;  Miscellaneous. 

No.  320.  Experiment  Station  Work  ;  Miscellaneous. 

No.  329.  Experiment  Station  Work ;  Miscellaneous. 

No.  332.  Nuts  and  their  Uses  as  Food. 

No.  342.  Experiment  Station  Work ;  Miscellaneous. 

No.  345.  Some  Common  Disinfectants. 

No.  348.  Bacteria  in  Milk. 

No.  358.  A  Primer  of  Forestry.     Part  II.  Practical  Forestry. 

No.  359.  Canning  Vegetables  in  the  Home. 

No.  363.  The  Use  of  Milk  as  Food. 

No.  367.  Lightning  and  Lightning  Conductors. 

No.  371.  Drainage  of  Irrigated  Lands. 

No.  374.  Experiment  Station  Work ;  Miscellaneous. 

No.  375.  Care  of  Food  in  the  Home. 

No.  377.  Harmfulness  of  Headache  Mixtures. 

No.  383.  How  to  Destroy  the  English  Sparrow. 

No.  389.  Bread  and  Bread  Making. 

No.  391.  Economical  Use  of  Meat  in  the  Home. 

No.  393.  Habit-forming  Agents. 

No.  406.  Soil  Conservation. 

No.  408.  School  Exercises  in  Plant  Production. 

No.  409.  School  Lessons  in  Corn. 

No.  410.  Potato  Culls  as  a  Source  of  Industrial  Alcohol. 

No.  413.  The  Care  of  Milk  and  its  Use  in  the  Home. 

No.  423.  Forest  Nurseries  for  Schools. 

No.  428.  Testing  Farm  Seeds  in  the  Home  and  in  the  Rural  School. 

No.  429.  Industrial  Alcohol :  Sources  and  Manufacture. 

OFFICE  OF  EXPERIMENT  STATION 
No.  101.   The   Selection   and   Installation   of  Machinery   for   Small 

Pumping  Plants. 
No.  162.   The  Influence  of   Cooking  upon  the   Nutritive   Value  of 

Meats. 


XXVlll  PUBLICATIONS 

BUREAU  OF  SOILS 
Bulletin  73.   Studies  in  Soil  Oxidation. 

BUREAU  OF  ANIMAL  INDUSTRY 

Bulletin  56.  Facts  Concerning  the  History,  Commerce,  and  Manu- 
facture of  Butter. 

Circular  131.   Designs  for  Dairy  Buildings. 

Circular  158.  Improved  Methods  for  the  Production  of  Market  Milk 
by  Ordinary  Dairies. 

REPRINTS  FROM  YEARBOOK 

DEPARTMENT    OF    AGRICULTURE 

1900.  Amplification  of  Weather  Forecasts. 

1903.  The  Relation  of  Forests  to  Stream  Flow. 

1905.  How  to  Grow  Young  Trees  for  Forest  Planting. 

1906.  New  Problems  of  the  Weather. 

1907.  The  Weather  Bureau  and  the  Public  Schools. 

1908.  The  Manufacture  of  Flavoring  Extracts. 
1908.  Soil  Mulches  for  Checking  Evaporation. 

1908.  Plant  Food  Removed  from  Growing  Plants  by  Rain  and  Dew. 

1908.  The  So-called  Change  of  Climate  in  the  Semiarid  West. 

1908.  The  Wastes  on  the  Farm. 

1909.  Comforts  and  Conveniences  in  Farmers'  Homes. 

FOREST  SERVICE 

Bulletin  36.   The  Woodman's  Handbook. 
Circular  114.    Wood  Distillation. 
Circular  130.   Forestry  in  the  Public  Schools. 
Circular  139.   A  Primer  of  Wood  Preservation. 

WEATHER  BUREAU 

No.  235.   Psychrometric  Tables  for  Obtaining  the  Vapor  Pressure, 

Relative  Humidity,  and  Temperature  of  the  Dew  Point. 
No.  285.   Measurement  of  Precipitation. 


PUBLICATIONS  XX  ix 

Bulletin  311.   Climate:  Its  Physical  Basis  and  Controlling  Factors. 
No.  312.   Invariability  of  our  Winter  Climate. 

Explanation  of  the  Weather  Map. 

Classification  of  Clouds.     With  Chart. 

Photomicrographs  of  Snow  Crystals. 

BUREAU  OF  PLANT  INDUSTRY 
Circular  71.   Legume  Inoculation  and  the  Litmus  Reaction  of  Soils. 


INTRODUCTION  TO  GENERAL  SCIENCE 


1.  EXPLOSIONS 

IF  we  take  a  little  gunpowder,  or  guncotton,  and  apply 
enough  heat  to  make  it  "catch  fire/'  the  material  will  burn 
in  a  flash.  If  it  is  unconfined,  it  will  burn  quietly.  On  the 
other  hand,  if  we  confine  it  in  a  proper  receptacle,  such  as  a 
gun  or  cannon,  and  ignite  it,  there  will  be  just  as  rapid  con> 
bustion  as  in  the  first  place.  Since  the  material  is  confined, 
however,  there  will  be  a  sudden  overcoming  of  this  restraint, 
producing  what  we  call  an  explosion. 

Take  a  little  ether  on  a  pellet  of  cotton,  place  it  on  a 
plate,  and  touch  a  burning  match  to  it.  The  ether  will  burn 
rapidly,  although  quietly.  Put  more  ether  upon  another 
pellet  of  cotton  and  place  it  in  a  wide-mouthed  pint  jar. 
Place  a  glass  plate,  over  the  top  of  the  jar  and  invert  three 
or  four  times.  Then  cautiously  slide  the  plate  to  one  side 
and  light  the  mixture  of  ether  and  air.  An  explosion  is  the 
result. 

Take  a  brass  tube  six  inches  long  and  one  inch  in  diameter. 
In  one  end  place  a  tightly  fitting  cork  stopper  in  which  there 
are  two  copper  wires,  separated,  but  approaching  each  other 
to  one  sixteenth  of  an  inch  at  that  end  of  the  stopper  which 
is  inside  of  the  tube.  Attach  an  induction  coil,  giving  at 
least  one  quarter  of  an  inch  spark,  to  the  other  ends  of  the 
copper  wires.  Make  a  small  swab  of  cotton  on  a  short 
stick  and  swab  out  the  "cannon,"  wetting  the  cotton  with 
B  1 


2  INTRODUCTION    TO   GENERAL  SCIENCE 

naphtha,  benzine,  ether,  alcohol,  and  gasoline,  in  turn.  Each 
time,  immediately  after  swabbing,  close  the  open  end  of  the 
•  cannon  with  another  stopper,  loosely  fitted,  and  explode  the 
mixture  by  means  of  electricity.  The  cork  will  be  driven 
forcibly  from  the  "cannon." 

We  conclude  that  if  anything  is  burnt  very  rapidly  in  an 
inclosed  space,  an  explosion  will  result.  The  conditions 
necessary  for  such  a  burning  will  be  discussed  in  Section  4, 
Combustion. 

References:  — 

1.  1703 : 16.  Explosion  of  Hydrogen. 

2.  1703 :  30.  Deflagration  the  Explanation  of  Explosions. 
a.    1704 : 196.  Explosions  in  Mines. 

6.    1708:111-112.   Explosion. 

c.  1709 : 30.  Gas  Explosion. 

d.  1711 : 286-287.  Mine  Explosions. 

2.  COMPOSITION  OF  MATTER  —  DEFINITION  OF  HEAT 

There  are  many  facts  which  indicate  that  all  matter  is 
made  up  of  small  particles  called  molecules,  and  that  these 
molecules  are  in  constant  motion.  If  they  move  fast,  we  say 
that  the  body  is  warm,  and  if  we  touch  the  body,  we  receive 
the  sensation  of  heat.  If  we  apply  heat  to  a  body,  the  mole- 
cules move  faster ;  if  by  any  means  we  "make  the  molecules 
move  faster,  the  body  is  warmer.  If  we  hammer,  rub,  or  in 
any  way  disturb  the  molecules,  the  body  becomes  hotter. 
We  have  merely  to  rub  our  hands  together  to  realize  this, 
and  we  are  all  familiar  with  the  fact  that  a  piece  of  lead, 
when  hammered,  becomes  very  hot.  When  these  molecules 
move  about,  it  is  quite  apparent  that  they  need  more  room 
than  if  they  had  remained  still ;  therefore  nearly  all  bodies, 


STATES  OP  MATTER  3 

when  heated,  expand  and  occupy  more  space.  See  Section 
15,  Expansion  Due  to  Heat.  We  make  use  of  the  expansion 
of  mercury,  in  the  thermometer,  to  indicate  the  degree  of 
heat.  See  Section  16,  Temperature  and  its  Measurement. 

References :  — 

1.  1703 : 127-128.  The  Molecular  Theory. 

2.  1803  :  82-83.  Nature  of  Matter. 

3.  1803:174-176.  Nature  of  Heat. 
a.   1801 :  253.  Nature  of  Heat. 
6.    1802:2-4.  Matter. 

c.  1804:247-248.     Nature  of  Heat. 

d.  1805 :  306-307.     Heat  and  Energy. 

e.  1806 :  299-300.     Theory  of  Heat. 

/.  1806 :  301.  Relation  of  Heat  and  Temperature. 

g.  1807 : 161-162.  Theories  of  Heat. 

h.  1808 :  206.  Definition  of  Heat. 

i.  1809 : 152-154.  Nature  and  Production  of  Heat. 

Experiments  (for  the  teacher)  in  1803  indicate  the  molec- 
ular constitution  of  solids,  liquids,  and  gases. 


3.  STATES  OP  MATTER 

All  material  exists  in  at  least  one  of  the  following  states : 
If  the  material  has  a  shape  which  it  *  can  maintain,  we 
call  it  a  solid.  If  its  shape  is  dependent  upon  the  vessel  in 
which  it  is  held,  we  give  the  name  liquid  to  it.  Finally,  if 
the  material  is  neither  solid  nor  liquid,  but  exists  either  in 
an  invisible  form  or  in  a  colored,  vaporous  condition,  we  call 
it  a  gas  or  a  vapor.  In  a  given  kind  of  material  the  only 
difference  between  a  solid  and  a  liquid  is  that  the  liquid  has 
more  heat  in  it  than  the  solid,  and  likewise  the  gas  has  more 


4  INTRODUCTION  TO  GENERAL  SCIENCE 

heat  in  it  than  the  liquid.  For  a  given  temperature  matter 
exists  in  only  one  of  these  conditions,  although  a  slight 
variation  of  temperature  may  cause  it  to  change  into  another 
state.  All  matter  existing  in  the  sun  is  so  hot  as  to  be  en- 
tirely composed  of  gas. 

There  is  one  material  with  which  we  are  all  familiar,  that 
exists  in  the  three  states  with  a  very  slight  change  of  tem- 
perature. Water,  above  thirty-two  degrees  F.,  and  below 
two  hundred  and  twelve  degrees  F.,  exists  as  a  liquid ;  below 
thirty-two  degrees  F.  it  is  a  solid;  above  two  hundred  and 
twelve  degrees  F.  it  is  a  vapor.  On  account  of  the  easy 
changing  from  one  condition  to  another,  water  is  a  powerful 
agent  in  the  transmission  of  energy.  We  shall  see  how  the 
freezing  of  water  can  break  rocks,  on  account  of  its  expansion. 
Boiling  water  also  exerts  a  tremendous  pressure,  and  thus 
enables  us  to  change  heat  into  mechanical  energy.  In  all  of 
the  explosions  solids  or  liquids  were  changed  into  gases  which 
occupied  much  more  space  than  the  solids  or  the  liquids. 
If  the  space  were  occupied  without  resistance,  there  was  a 
rapid,  but  quiet,  burning ;  otherwise  the  space  was  occupied 
with  force,  and  an  explosion  resulted. 

References :  — 

1.  1304 : 18-19.  Air,  Water,  Rock. 

2.  1703  : 128.  The  Physical  States  of  Matter. 

3.  1803  :  105-106.  The  Three  States  of  Matter. 

a.  1201 :  126-128.     Gases,  Liquids,  and  Solids. 

b.  1302:  26.  Rock,  Water,  and  Air. 

c.  1804 :  127-129.      The    Peculiar    Properties    of    the   Three 

States  of  Matter. 

d.  1805 :  101-105.      States  of  Matter  Explained. 

e.  1806 :  347-349.      Causes  of  Changes  of  State. 
/.    1806  :  354-355.       Causes  of  Changes  of  State. 
g.   1807 :  3-5.  The  Three  States  of  Matter. 


COMBUSTION  5 


4.   COMBUSTION 

We  have  seen  that  in  explosions  the  burning  took  place 
rapidly,  and  throughout  the  whole  mass  at  the  same  time. 
Explosions  are,  however,  only  one  kind  of  chemical  action 
which  is  called  combustion.  We  are  all  familiar  with  the 
combustion  which  occurs  in  fireplaces,  stoves,  and  lamps. 
This  is  called  ordinary  combustion,  because  we  are  familiar 
with  it,  but  the  most  common  sort  of  combustion  is  not 
generally  recognized. 

Before  considering  the  kinds  of  combustion  it  might  be 
well  to  understand  what  this  phenomenon  really  is. 

Experiment  i.  —  Ordinary  Combustion. 

Apparatus :  Argand  lamp  chimney,  cork  stopper  to  fit  bot- 
tom of  chimney  and  one  to  fit  top  of  chimney,  wire  nail 
about  one  inch  long,  small  pan  or  saucer. 

Materials :  Piece  of  candle  about  two  inches  long,  matches. 

a.  Cut  notches  on  side  of  larger  cork  so  that  the  amount 
removed  is  about  one  third  of  the  cork,  push  nail  through 
the  center  of  the  cork  and  stick  the  candle  on  it.  Then  light 
candle  and  let  it  burn  in  the  open  air. 

Note  waviness  of  the  flame  and  the  tendency  to  smoke. 
Why  is  the  flame  wavy  ? 

6.  While  the  candle  is  burning,  lower  the  Argand  chimney 
over  it,  and  push  the  chimney  down  over  half  the  length  of  the 
cork. 

Is  the  flame  different  now  ?  Describe  the  difference.  What 
makes  the  difference  ? 

c.  Push  the  chimney  down  over  the  whole  of  the  cork,  so 
that  the  bottom  of  the  chimney  rests  on  the  table,  and  then 
put  the  other  cork  into  the  top  of  the  chimney. 


6  INTRODUCTION   TO   GENERAL  SCIENCE 

What  happens?  Why?  Does  it  happen  immediately? 
Why? 

d.  Remove  top  cork,  remove  candle,  light,  it  and  return  it 
to  the  chimney,  pushing  in  bottom  cork,  halfway,  as  at  first. 
Place  bottom  of  chimney  in  a  saucer  nearly  filled  with  water, 
and  immediately  insert  top  cork. 
'  What  happens?     Why? 

We  conclude  that  combustion  is  concerned  with  two  things,  — 
the  material  to  be  burnt,  called  the  combustible,  and  something 
which  aids  the  combustion,  called  the  supporter  of  combustion. 

Returning  now  to  the  matter  of  combustion  in  general,  we 
can  state  that  it  is  the  chemical  union  of  at  least  two  materials, 
the  combustible  and  the  supporter  of  combustion.  Where 
this  union  is  rapid,  we  have  the  ordinary  combustion.  When 
the  combustible  and  supporter  of  combustion  are  thoroughly 
mixed,  we  have  the  proper  conditions  for  an  explosion.  Yet 
the  union  is  not  always  rapid;  it  may  be  very  slow.  Thj 
rusting  of  iron  and  the  decay  of  wood  are  examples  of  slow 
combustion.  The  most  common  supporter  of  combustion  is 
oxygen,  which  comprises  about  one  fifth  of  the  atmosphere. 
Whenever  combustion  takes  place,  whether  it  is  ordinary  or 
slow,  heat  is  produced.  In  the  case  of  many  examples  of  slow 
combustion  the  heat  escapes  and  cannot  be  perceived.  Some- 
times the  heat  does  not  escape,  but  accumulates  gradually 
until  the  material  is  hot  enough  to  produce  ordinary  combus- 
tion without  the  application  of  exterior  heat.  We  call  this 
spontaneous  combustion. 

Experiment  2.  —  Spontaneous  Combustion. 
Apparatus :  Ring  stand,  or  wire  ring  four  inches  in  diam- 
eter, supported,  test  tubes,  tweezers. 

Materials :  Phosphorus  cut  under  water  into  pieces  half  the 


COMBUSTION  7 

size  of  a  pea,  and  kept  under  water,  carbon  bisulphide,  filter 
paper. 

a.  Pour  1  c.c.  of  carbon  bisulphide  into  a  test  tube  and  drop 
in  a  piece  of  phosphorus  which  has  been  dried  with  a  filter 
paper.  Do  not  touch  the  phosphorus  with  the  hands,  or  rub 
it.  As  soon  as  the  phosphorus  has  dissolved,  pour  the  solu- 
tion on  a  clean  piece  of  filter  paper  and  place  the  paper  on  the 
ring.  When  the  carbon  bisulphide  has  evaporated,  the  phos- 
phorus on  the  paper  will  burst  into  a  flame. 

6.  Repeat  (a),  but  place  filter  paper  on  a  piece  of  iron  — 
the  flat  base  of  the  ring  stand.  What  happens  ?  Why  ? 

Phosphorus  combines  very  readily  with  the  oxygen  of  the 
air.  In  the  above  experiment  the  phosphorus  is  spread  over 
a  large  surface,  so  that  the  oxygen  comes  into  contact  with  a 
considerable  amount  of  it  at  one  time.  Thus  a  large  quan- 
tity of  heat  is  soon  produced.  The  heat  does  not  escape 
from  the  paper,  since  the  latter  rests  on  the  ring,  and  is  not 
in  contact  with  anything  else.  Therefore  the  temperature 
of  the  paper  rises,  and  ordinary  combustion  takes  place. 
Oily  rags,  damp  leaves  or  hay,  and  other  material  subject  to 
slow  decay  may  set  fire  to  buildings  through  spontaneous 
combustion.  Proper  ventilation  will  aid  in  p/eventing  danger. 

References :  — 

1.  1703 :  31-32.    Combustion  —  Slow  and  Spontaneous. 

2.  Farmers'  Bulletin  No.  105 :  26-27.     Spontaneous  Combustion 

of  Hay. 

a.  1701:17-18.  Combustion. 

6.  1702:49-50.  Combustion. 

c.  1704  :  17.  Definition  of  Combustion. 

d.  1707  :  37.  Definition  of  Combustion. 

e.  1708  :  48-49.  Combustion  and  Oxidation. 
/.  1711:51-57.  Combustion  in  General. 

g.    1713  :  51-52.     The  Phlogiston  Theory. 


8  INTRODUCTION   TO  GENERAL  SCIENCE 

5.    OXYGEN  —  ITS  USES  AND  ACTION 

Oxygen  means  acid-producing  material,  and  it  is  found  in 
nearly  all  the  acids.  Its  use  in  the  atmosphere,  of  which  it 
composes  about  one  fifth,  is  to  support  combustion.  There 
can  be  no  ordinary  burning  without  the  presence  of  oxygen. 
The  oxygen  combines  with  the  carbon  in  the  wood,  coal,  or 
other  combustible,  producing  carbon  dioxide,  which  passes 
off  as  a  gas.  It  is  the  combination  of  the  carbon  and  oxygen 
which  produces  the  heat  we  obtain  from  our  fires.  Oxygen 
also  causes  the  slow  combustion  which  takes  place  in  animals, 
producing  animal  heat,  and  burning  up  waste  material  ab- 
sorbed by  the  blood.  When  water  is  thrown  on  the  fire,  it 
puts  the  fire  out,  simply  because  the  water  lowers  the  tem- 
perature of  the  burning  substance  and  forms  a  film  upon  it 
which  prevents  the  access  of  oxygen.  Similarly,  carbon 
dioxide  bombs,  which  are  exploded  to  extinguish  fires,  keep 
out  oxygen,  because  the  carbon  dioxide  is  heavier  than  the 
oxygen  and  coats  the  surface  of  the  combustible.  See  Section 
90,  The  Chemical  Engine. 

Experiment   3.  —  Oxygen   and   Combustion. 

Apparatus:  Test  tube  8"  X  I",  stopper,  with  one  hole  to 
fit  test  tube,  test-tube  holder,  or  clamp,  ring  stand,  glass  tube 
3"  long,  rubber  tube  12"  long,  bread  pan  (pneumatic  trough), 
four  wide-mouthed,  half-pint  bottles,  tweezers,  deflagrating 
spoon,  lamp,  four  glass  plates  4"  X  4". 

Materials:  Powdered  potassium  chlorate,  granulated 
manganese  dioxide,  wood  splinters,  charcoal  in  small  pieces, 
powdered  sulphur,  iron  picture  cord,  magnesium  ribbon, 
phosphorus. 

a.  Mix  equal  parts  of  potassium  chlorate  and  manganese 


OXYGEN  9 

dioxide  (about  a  tablespoonful  in  all)  on  a  piece  of  paper,  and 
then  pour  them  into  the  test  tube.  Insert  glass  tube  in  cork, 
place  in  test  tube,  and  hold  test  tube  by  ring  stand  obliquely. 
Place  rubber  tube  over  glass  tube,  and  put  other  end  of  rubber 
tube  under  the  mouth  of  a  bottle  which  has  been  filled  with 
water  and  inverted  in  the  pneumatic  trough,  which  should  be 
half  full. of  water.  Heat  the  test  tube  slowly.  A  gas  will  soon 
come  off  and  fill  the  bottle.  This  gas  is  oxygen.  Collect  four 
bottles  of  gas,  and  cover  each,  when  full,  with  a  glass  plate. 

6.  Light  a  splinter  of  wood  and  then  blow  out  the  flame, 
obtaining  a  glowing  coal  on  the  splinter.  Insert  this  in  a 
bottle  of  oxygen.  What  happens  ? 

c.  Take  a  piece  of  picture  cord  6"  long,  hold  it  with  tweezers 
by  one  end,  dip  the  other  end  in  sulphur,  and  light  the  sulphur. 
When  you  get  some  burning  sulphur  on  the  wire  cord,  insert 
it  in  a  second  bottle  of  oxygen.     Describe  the  results. 

d.  Burn  a  piece  of  magnesium  ribbon  partly  in  air,  but 
mostly  in  oxygen.     Conclusions? 

e.  Burn  charcoal  in  air  and  in  oxygen.     Note  that  there 
is  no  flame. 

The  results  of  this  experiment  strengthen  our  conclusion 
in  Experiment  1,  that  the  act  of  combustion  requires  the 
presence  of  some  substance  from  the  air.  We  see  that  oxygen 
produces  the  same  results  as  air,  but  much  more  vigorously, 
because  it  is  not  diluted  with  other  gases  which  are  present  in 
the  atmosphere.  Where  there  is  a  sufficient  supply  of  oxygen, 
there  is  complete  combustion  and  no  smoke.  Smoke  always 
indicates  unburned  fuel,  and  therefore  means  waste. 
References :  — 

1.    1703  :  24-29.        Oxygen :  Its  Preparation  and  Characteristics, 
a.    1612  :  9-10.     Oxygen  in  the  Soils. 
6.   1612 :  53-54.   Properties  of  Oxygen. 


10  INTRODUCTION   TO   GENERAL  SCIENCE 

c.  1701 :  13.          Nature  of  Oxygen. 

d.  1701 :  16-21.   Properties  of  Oxygen  and  Combustion. 

e.  1702  :  31-36.   Oxygen  —  Preparation,  Properties,  and  Im- 

portance. 

/.  1706:11-18.     Oxygen  and  its  Relation  to  Life. 

g.  1707  :  36-43.     Oxygen  and  Combustion. 

h.  1709 :  19-24.    Oxygen  and  Combustion. 


6.    FUELS 

The  material  which  combines  with  oxygen  in  any  combus- 
tion is  called  fuel.  There  are  solid,  liquid,  and  gaseous  fuels, 
but  all  contain  a  common  material  —  carbon. 

The  most  universal  fuel  is  wood.  This  is  a  compound  made 
by  growing  plants,  and  consists  chiefly  of  carbon  and  water 
combined. 

The  other  solid  fuels  are  the  various  kinds  of  coal,  which 
will  be  considered  in  Section  137. 

Liquid  fuels  are  kerosene,  gasoline,  alcohol,  naphtha,  ben- 
zine, ether,  turpentine,  and  other  oils.  They  are  all  com- 
pounds of  carbon. 

Gaseous  fuels  are  natural  gas,  artificial  gas,  and  the  vapors 
from  several  of  the  liquid  fuels.  All  of  the  fuels  will  be 
studied  in  Section  137,  Coal,  and  in  Section  138,  Petroleum, 
as  well  as  in  Section  28,  Destructive  Distillation. 

Rzferences:  — 

1.  1702:  115-116.          Fuels. 

2.  1710:23-32.  Fuels. 

a.  1701 :  399-400.     Petroleum  Products. 

b.  1704 :  203-205.     Fuels  from  Petroleum. 


GAS  AND   GASOLINE  ENGINES  11 


7.    BLASTING 

If  a  hole  in  a  ledge  of  rock,  or  the  stump  of  a  tree,  is  filled 
with  gunpowder  or  dynamite  packed  down  with  sand,  ignition 
of  the  powder  will  cause  an  explosion  and  considerable  local 
damage.  The  solid  powder  turns  instantly  to  gases,  which, 
due  to  their  nature  and  the  high  temperature,  occupy  an  enor- 
mous volume  compared  with  the  solid  from  which  they  came. 
This  sudden  expansion  causes  the  breaking  and  rending  of  the 
surrounding  material. 

The  question  which  very  naturally  arises  is :  Why  does  the 
powder  burn  when  there  is  apparently  no  air,  or  oxygen, 
present  ?  We  have  learned  that  oxygen  must  be  present  in 
other  cases  of  combustion,  and  this  example  is  no  exception. 
The  chemicals  of  which  the  powder  is  made  contain  the  oxy- 
gen in  just  the  right  proportion  to  produce  complete  combus- 
tion, and  it  is  so  thoroughly  blended  that  the  combustion  takes 
place  throughout  the  whole  mass  at  the  same  time.  This 
kind  of  combustion  is  called  deflagration.  The  smoke  of 
powder  is  not  carbon,  but  is  due  to  the  formation  of  a  small 
amount  of  solid  matter.  Where  no  solid  matter  is  formed, 
we  have  smokeless  powder. 

References :  — 

1.    1703:30.  Deflagration, 

a.    1704:307-308.     Gunpowder. 
6.    1705  : 180.  Nitroglycerine  and  Guncotton. 

c.    1707:331-333.     Gunpowder. 
Also  see  references  under  Section  1. 

8.    GAS  AND  GASOLINE  ENGINES 

Blasting  is  only  one  of  the  uses  we  make  of  explosions.  If 
the  explosions  are  limited,  or  controlled,  and  one  part  of  the 


12  INTRODUCTION   TO  GENERAL  SCIENCE 

container  is  free  to  move,  we  can  change  the  force  of  the  ex- 
plosion into  rotary  motion,  as  in  the  gas  engine.  Here  a 
mixture  of  gas  and  air,  in  the  right  proportions  for  complete 
combustion,  is  drawn  into  a  cylinder  by  the  forward  stroke 
of  the  piston,  compressed  by  the  return  stroke,  and  finally 
exploded,  thus  pushing  the  piston  forward  with  great  energy. 
It  is  then  forced  out  upon  the  return  of  the  piston.  This  is 
the  so-called  four-cycle  gas  engine. 

In  the  two-cycle  engine  the  back  stroke  of  the  piston  causes 
a  partial  vacuum  in  the  crank  case,  which  is  inclosed,  and  a 
mixture  of  gas  and  air  is  drawn  in.  The  forward  stroke  of 
the  piston  forces  this  mixture  up  into  the  cylinder,  the  fresh 
mixture  pushing  out  the  burnt  gases  and  being  compressed 
at  the  return  of  the  piston.  The  explosion  then  takes  place 
and  forces  the  piston  forward.  The  incoming  fresh  mixture 
forces  out  the  old  burnt  mixture. 

References :  — 

1.  1803 : 191-194.         The  Principle  of  the  Gas  Engine. 

2.  Farmers'  Bulletin  No.  277 :  The  Use  of  Alcohol  and  Gasoline 

in  Farm  Engines. 

a.  1607 :  522-530.    Gasoline  Engines. 

b.  1801 :  299-300.    The  Gas  Engine. 

c.  1802 :  322.  The  Gas  Engine. 

d.  1809 :  208-210.   International  Combustion,  or  Gas  Engines. 

e.  1810 : 193-196.    The  Gas  Engine. 

9.    ANIMAL  HEAT 

We  call  the  heat  produced  by  slow  combustion  of  food 
within  the  body,  animal  heat.  This  combustion,  while  slow, 
is  perfect.  All  of  the  carbon  in  food  is  completely  combined 
with  oxygen,  and  its  combustion  causes  no  smoke.  Com- 
bustion likewise  takes  place  within  the  lungs,  and  moreover, 


ANIMAL   HEAT  13 

the  red  corpuscles  of  the  blood  absorb  the  oxygen,  which 
we  inhale,  and  carry  it  to  all  parts  of  the  body,  to  burn  up 
waste  material.  Thus  it  is  that  all  parts  of  the  body  are  warm. 
If,  however,  the  circulation  is  poor,  so  that  this  destruction 
of  waste  is  not  complete,  we  have  cold  feet,  cold  hands,  and, 
in  very  severe  cases  of  poor  circulation,  bad  chills. 

The  temperature  of  human  beings  is  ninety-eight  and  four 
tenths  degrees  F.  No  matter  what  the  weather  may  be,  the 
temperature  of  a  healthy  person  does  not  vary  more  than  one 
half  of  a  degree.  A  variation,  upward  or  downward,  of  a  few 
degrees  from  the  normal  temperature  will  result  in  death. 
Thus  it  is  that  fevers  and  chills  are  weakening  to  the  consti- 
tution, and,  unless  properly  taken  care  of,  may  be  fatal. 

If  we  become  cold,  we  may  exercise  and  increase  the  circu- 
lation, thereby  increasing  the  combustion  throughout  the 
whole  body,  and  maintaining  the  temperature  which  would 
otherwise  be  lowered.  Or,  if  we  desire,  we  put  on  heavier 
clothes,  which  serve  to  keep  in  the  heat  of  the  body.  If  we 
become  warm,  we  remove  some  of  our  clothing. 

In  Section  89,  Carbon  Dioxide,  this  matter  will  be  considered 
further. 

References :  — 

1.  1503:348-349.  Blood  Temperature. 

2.  1503 :  398.  The  Bodily  Heat  as  Affected  by  Alcohol. 

3.  1703:11-12.  The  Kipp  Generator, 
a.    1506  :  32-33.  Oxidation  in  the  Body. 
6.    1507  :  48-49.  Amount  of  Animal  Heat. 

c.  1507  :  240.  Loss  of  Heat  from  the  Body. 

d.  1509:211-212.     Heat  of  the  Body. 

e.  1511 :  98-99.         Animal  Heat. 

Experiment  4.  —  Complete  and   Incomplete  Combustion. 
Apparatus :  Alcohol  lamp  having  a  collar  around  the  wick 


14  INTRODUCTION  TO  GENERAL  SCIENCE 

one  inch  high  with  an  inlet  tube  one  fourth  of  an  inch  in  diam- 
eter, a  one  pint  Kipp  generator,  rubber  tubing. 

Materials :    Turpentine,  sodium  peroxide  in  cubes. 

a.  Fill  alcohol  lamp  with  turpentine,  put  collar  around 
wick  and  connect  with  the  oxygen  generator.  Light  the  wick 
before  the  oxygen  is  turned  on,  and  notice  the  kind  of  flame 
which  is  produced.  Then  gradually  turn  on  the  oxygen  and 
note  the  change  which  takes  place  in  the  flame.  What  is 
smoke  ?  Why  is  it  formed  ? 

Sodium  peroxide,  when  combining  with  water,  forms  so- 
dium hydroxide  or  caustic  soda,  and  sets  free  oxygen.  To  use 
the  Kipp  generator,  place  a  few  pieces  of  sodium  peroxide  in 
the  middle  bulb,  put  the  parts  together,  and  pour  in  enough 
water  to  fill  the  lower  bulb  and  about  half  of  the  middle  bulb. 
When  the  outlet  is  closed,  the  gas  which  is  being  generated 
pushes  the  water  away  from  the  sodium  peroxide,  and  thus  the 
action  is  stopped  automatically. 

10.    FLAMES 

All  combustion  is  not  accompanied  by  flames.  Slow  com- 
bustion of  any  kind,  whether  in  chemicals,  in  decaying  matter, 
or  in  the  production  of  animal  heat,  does  not  produce  flame. 
It  is  only  where  the  temperature  is  high  enough  to  change  the 
solid  or  liquid  fuel  into  gas  that  flames  are  produced.  A 
flame,  then,  is  gas  in  combustion. 

In  Section  28,  Destructive  Distillation,  we  shall  see  that 
when  any  solid  or  liquid  combustible  is  heated,  part  of  its 
material  is  changed  into  gas.  The  experiments  will  show 
this  fact  in  relation  to  a  candle  flame. 

1.  1703:35-36.  Flames. 

2.  1703 :  214-219.          Structure  of  Flames. 


FIRST   AID  TO   THE  BURNT  15 

a.  1701:211-217.  Flames. 

6.  1704:  184-187.  Luminous  and  Nonluminous  Flames. 

c.  1705  :  54-56.  Experiments  with  Flames. 

d.  1707 :  204-208.  Flames  —  The  Safety  Lamp. 

e.  1708  :  107-109.  Flames. 

/.    1709  :  238-241.     Candle  and  Gas  Flames. 
g.    1712:319-321.     Flame. 

Experiment    5.  —  Source  of  Flames. 
Apparatus :  Piece  of  glass  tubing  6  inches  long. 
Materials:  Candle,  matches. 

a.  Light  candle  and  allow  it  to  burn  for  a  minute.  Then 
light  a  match,  and,  blowing  out  the  candle  flame,  immediately 
hold  the  burning  match  over  the  candlewick  a  distance  of 
about  half  an  inch.  What  happens?  Explain. 

6.  After  candle  has  been  burning  for  over  a  minute,  insert 
one  end  of  the  glass  tube  into  the  candle  flame,  at  a  very  slight 
angle  from  the  vertical.  Apply  lighted  match  to  the  other 
end  of  tube.  What  burns  ?  Where  did  the  material  come 
from? 

11.    FIRST  AID  TO  THE  BURNT 

Immediate  action  is  what  counts.  Where  the  clothing  is 
on  fire,  the  flames  should  be  slapped  out,  or,  if  a  large  amount 
of  the  clothing  is  burning,  the  person  should  be  wrapped  in  a 
mat  or  rug,  and  rolled  on  the  floor.  A  coat  may  be  used  in 
place  of  the  rug.  Always  keep  the  head  lower  than  the  rest 
of  the  body  to  avoid  inhalation  of  flames. 

When  burns  are  not  severe,  ordinary  baking  soda  may  be 
applied  after  the  burn  has  been  wet  with  warm  water,  to 
make  the  powder  stick.  Bandage  with  a  clean  cloth  which 
has  been  torn  into  strips  three  fourths  of  an  inch  wide. 

If  the  burns  are  serious,  the  following  method  may  be  used : 


16  INTRODUCTION  TO  GENERAL  SCIENCE 

Prick  with  a  sterilized  needle  any  water  blisters,  then  apply 
equal  parts  of  limewater  and  olive  oil.  Cover  burn  with 
absorbent  cotton  which  has  been  soaked  in  the  same  mixture, 
and  over,  this  place  dry  cotton.  Then  bandage.  Limewater 
may  be  prepared  by  putting  one  ounce  of  fresh  unslaked  lime 
into  a  pint  of  water,  shaking,  and  allowing  to  settle.  If  lime- 
water  is  not  at  hand,  use  baking  soda  and  olive  oil. 

White  lead,  mixed  into  a  thick  paste  with  linseed  oil,  may 
also  be  used.  Apply  with  a  soft  brush.  Any  of  the  following 
materials  may  be  applied,  but  as  quickness  means  much 
to  the  patient,  ease  in  obtaining  the  remedy  should  have  first 
consideration:  baking  soda,  olive  oil,  limewater,  white 
lead  and  linseed  oil,  powdered  chalk,  starch  (either  from 
potatoes  or  corn),  flour  of  any  kind,  and  mucilage  or  dissolved 
gelatine  covered  with  any  of  the  powders  mentioned  above. 

References :  — 

1.   1503  : 398.  Cuts,  Bruises,  and  Burns. 

a.    1505  :  24.  Treatment  of  Burns. 

6.    1506 :  298.  Burns  and  Scalds. 

c.  1507:248.  Burns. 

d.  1508:327.  Burns. 

e.  1511 :  375.  Burns  and  Scalds. 

12.    STERILIZATION  BY  HEAT 

When  we  break  the  skin  in  any  way,  the  protective  covering 
is  removed  and  our  bodies  are  open  to  the  attacks  of  small 
plants  called  bacteria.  Bacteria  produce  more  trouble  in 
a  wound  which  has  not  been  properly  taken  care  of  than  the 
injury  itself.  Sometimes  we  are  obliged  to  inflict  wounds 
upon  ourselves,  and  with  a  little  care  we  can  guard  against 
admitting  bacteria  unnecessarily. 

If  we  desire  to  remove  a  splinter,  or  open  a  pimple,  or  larger 


ANTISEPTIC   WASHES  17 

accumulation  of  pus,  we  should  be  careful  that  the  knife,  or 
needle,  has  no  bacteria  on  it.  The  needle  may  be  heated 
red-hot  and  used  as  soon  as  cool,  with  perfect  safety.  The 
same  treatment  would  ruin  a  knife,  however,  and  the  latter 
should  be  boiled  for  twenty  minutes  to  secure  absolute  steril- 
ization, although  two  or  three  minutes  will  be  long  enough  in 
most  cases.  Sterilization  may  be  thought  of  as  the  removal 
of  undesirable  bacteria.  Thus  cooking  food  protects  us,  as 
there  may  be  harmful  bacteria  present  which  will  be  killed 
by  the  heat. 
References :  — 

1.  1710 : 113.  Effect  of  Steam  upon  Germs. 

2.  1901 :  110-112.  Death  Temperature  of  Bacteria. 

3.  1901 :  191-196.  Pasteurization. 

a.  1505  :  162-164.  Protection  against  Disease  Germs. 

6.  1507 :  73.  Sterilization  and  Disinfection. 

c.  1508  :  80.  Pasteurization. 

d.  1902 : 171-176.  Sterilization  and  Pasteurization. 

13.    ANTISEPTIC  WASHES  —  DISINFECTANTS 

We  know  that  when  we  have  a  cut  or  bruise,  bacteria  of 
disintegration  and  disease  may  enter  and  attack  it.  In  this 
event  a  large  scab  is  formed,  and  often  the  place  becomes  a 
running  sore.  We  know  that  this  scab  and  the  oozing  ma- 
terial are  composed  wholly  of  dead  white  corpuscles,  which 
have  lost  their  lives  fighting  with  bacteria.  On  the  other 
hand,  if  we  treat  a  cut  or  bruise  with  some  antiseptic, 
which  tends  to  kill  all  harmful  bacteria,  the  wound  will 
get  well  without  any  large  scab,  and  without  any  oozing  of 
pus.  Perhaps  the  best  agent  we  can  use  for  this  purpose, 
and  the  handiest,  is  corrosive  sublimate.  It  comes  in 
tablets,  of  such  a  size  that  the  solution  of  one  tablet  in  a 
c 


18  INTRODUCTION  TO  GENERAL  SCIENCE 

pint  of  water  gives  the  right  strength  for  disinfecting  pur- 
poses. If  a  cut  is  bathed  immediately  with  this  solution,  it 
will  get  well  in  a  wonderfully  short  time. 

It  is  well  to  recognize  the  fact  that  there  are  harmful  bac- 
teria and  to  guard  ourselves  against  them.  Nevertheless,  we 
should  not  live  in  constant  fear  of  them.  The  best  way  to 
escape  the  attacks  of  bacteria  is  to  maintain  our  bodies  in  a 
healthful  condition.  To  do  this,  we  should  have  a  proper 
amount  of  sleep,  eat  a  sufficient  quantity  of  healthful  food, 
exercise,  and  avoid  excesses  of  any  kind. 

In  order  to  have  healthful  food  and  live  in  healthful  houses, 
disinfectants  should  be  used  whenever  our  sense  of  smell 
notifies  us  that  there  is  decay  around  us.  On  the  other  hand, 
there  may  be  times  when  it  becomes  necessary  to  use  disin- 
fectants, even  if  there  is  no  unpleasant  odor.  To  clean  a 
building  or  a  sick  room  thoroughly,  several  disinfectants  may 
be  used.  Chloride  of  lime  and  carbolic  acid  are  favorites  with 
many,  chiefly  because  they  have  a  "  clean  "  smell.  They  are 
not  nearly  as  effective  as  the  burning  of  sulphur  or  the  use  of 
formaldehyde,  or  potassium  permanganate  and  formaldehyde 
together. 

References :  — 

1.  1503 : 171-172.  Prevention  of  Bacterial  Diseases. 

2.  1710:108-116.  Disinfectants,  etc. 

3.  1901  :  255-261.  Disinfectants. 
a.    1506:274-278.  Disinfection. 
6.   1509:290-292.  Disinfection. 

c.  1511 :  376-379.      Disinfectants  and  How  to  Use  Them. 

d.  1902  :  323-326.      Disinfectants  and  their  Application. 

e.  1904 :  158-163.      Disinfection  and  Disinfectants. 

4.  Farmers'  Bulletin  No.  345.     Some  Common  Disinfectants. 


EXPANSION  DUE  TO  HEAT  19 

14.    CHEMICAL  EFFECTS  OF  HEAT 

When  the  various  combustibles  united  with  oxygen  and 
burned  quietly,  or  exploded,  we  had  examples  of  chemical 
action.  We  learned  that  heat  starts  chemical  action.  After 
the  action  begins,  it  gives  off  heat.  In  Section  31  we  shall 
study  chemical  action  as  a  source  of  heat. 

If  we  remember  that  heat  is  the  motion  of  molecules,  and 
that  they  not  only  move,  but  strike  against  their  neighbors, 
we  can  see  that  this  motion,  if  increased,  would  make 
them  strike  harder,  and  even  unite  with  some  other  dis- 
similar molecules.  Thus  it  is  that  heat  aids  chemical  action. 

Heat  produces  several  very  complex  changes  in  meat  and 
other  substances  which  have  had  life,  and  these  changes  make 
the  substances  more  suitable  for  food.  Heat  also  causes 
chemical  changes  in  food  which  are  very  similar  to  the  pro- 
cesses of  digestion.  Thus  boiling  starch  slowly  changes  it 
into  a  sugar.  See  Section  29,  Cooking. 

References :  — 

1.  1703 :  24.  Heat  Liberates  Gases  from  Compounds. 

2.  1703  :  428.  Effect  of  Heat  on  Starch. 

3.  1901 :  36.  Heat  Aids  Plant  Growth. 

a.  1507  :  53-55.  Effects  of  Heat  on  Food. 

b.  1708 :  35.  Combination  Caused  by  Heat. 

c.  1709  :  2-3.  Effect  of  Heating  a  Metal  in  Air. 

d.  1711 :  24-27.  Physical  and  Chemical  Effects  of  Heat. 

15.    EXPANSION  DUE  TO  HEAT 

The  first  effect  of  heat  on  a  body  is  to  cause  its  molecules 
to  move  faster.  Since  these  hit  against  their  neighbors,  and 
are  in  turn  hit  by  them,  the  body  as  a  whole  becomes  larger, 
and  we  say  that  expansion  has  taken  place.  The  only  ma- 


20  INTRODUCTION   TO  GENERAL  SCIENCE 

terial  which  seems  to  contract  when  heated,  is  rubber ;  this 
shortens,  although  its  volume  increases. 

While  we  generally  notice  the  expansion  of  a  body  in  one 
direction  only,  that  is,  linear  expansion,  it  must  not  be  for- 
gotten that  a  body  expands  in  three  dimensions.  If  we  know 
the  linear  expansion  of  a  body,  however,  we  can  easily  cal- 
culate the  cubical  expansion,  as  the  increase  for  the  same 
change  in  temperature  is  always  proportional  to  the  length. 

Not  only  do  solids  expand,  but  the  same  is  true  of  liquids 
and  gases.  The  expansion  of  liquids  and  gases  gives  rise  to 
many  phenomena  which  will  be  described  in  other  sections. 

References :  — 

1.  1803  :  89.  Expansion  of  Liquids. 

2.  1803  : 104.  Expansion  of  Solids. 

3.  1803  :  144.  Unequal  Expansion  of  Solids. 

a.  1801 :  261-263.  Expansion  of  Solids,  Liquids,  and  Gases. 

6.  1802 :  294-298.  Expansion  Due  to  Heat. 

c.  1804 :  265-270.  Effects  of  Heat  Expansion. 

d.  1805  :  297-302.  Expansion  and  its  Applications. 

e.  1806 :  322-324.  Applications  of  Expansion. 

/.    1807  :  177-178.      Effects  and  Applications  of  Expansion. 

Experiment  6.  —  Expansion  Due  to  Heat. 

Apparatus :  Glass  bulb  tube,  flask  100  c.c.,  two-hole  rubber 
stopper,  thermometer,  glass  tube  3  feet  long,  ring  stand, 
asbestos  mat  5"  X  5",  lamp,  two  iron  screw  eyes,  one  of  which 
will  just  pass  through  the  other,  two  pieces  of  wood  for  handles. 

a.  Put  bulb  tube  through  one  hole  of  stopper  and  insert  in 
flask,  half  filled  with  water;  place  hand  on  bulb.     What  hap- 
pens?   Warm  bulb  very  gently  with  lamp.    What  happens? 
Let  bulb  cool,  and  explain  what  takes  place. 

b.  Place  the  thermometer  in  one  of  the  holes  of  the  stopper 
and  the  glass  tube  in  the  other.     Fill  the  flask  full  of  water 


TEMPERATURE  AND  ITS  MEASUREMENT         21 

and  insert  the  stopper.  This  will  cause  the  water  to  run  up 
the  tube  a  short  distance.  Place  flask  over  the  asbestos  mat, 
on  ring  stand,  and  heat  slowly.  Should  you  say  that  expan- 
sion is  proportional  to  the  change  in  temperature  ? 

c.  Screw  each  screw  eye  into  a  piece  of  wood  to  serve  as 
handles.  Heat  the  smaller  screw  eye,  and  then  see  if  it  will 
pass  through  the  larger  screw  eye.  State  two  methods  which 
may  be  employed  to  enable  you  to  accomplish  this.  Tell 
what  would  be  the  result  if  you  had  placed  the  larger  screw 
eye  in  some  freezing  mixture  instead  of  heating  the  smaller 
screw  eye. 

16.    TEMPERATURE  AND  ITS  MEASUREMENT 

In  considering  heat,  we  learned  that  it  was  due  to  the  mo- 
tions of  the  molecules  of  a  body.  If  one  body  is  giving  heat 
to  another  body,  we  say  that  the  intensity  of  heat  of  the  first 
body  is  greater  than  that  of  the  second  body.  This  intensity 
of  heat  is  called  temperature,  and,  as  has  been  stated,  tem- 
perature is  usually  measured  by  the  expansion  of  some 
material.  Mercury  is  the  material  used  for  ordinary  tem- 
peratures, as  its  expansion  is  almost  proportional  to  change 
in  temperature,  but  colored  alcohol  is  used  for  temperatures 
which  are  very  low,  while  in  extreme  cases  the  gas  thermome- 
ter is  used. 

There  are  two  scales  of  temperature,  the  "  Fahrenheit/7 
and  the  "  Centigrade  "  or  "  Celsius."  'In  the  Fahrenheit 
scale,  thirty-two  degrees  is  arbitrarily  taken  as  the  freezing 
point  of  water,  and  two  hundred  and  twelve  degrees  as  the 
boiling  point  of  water.  Zero  is  merely  thirty-two  degrees 
below  the  freezing  point.  In  the  Centigrade  thermometer, 
zero  is  taken  as  the  freezing  point,  and  one  hundred  degrees 


22  INTRODUCTION  TO  GENERAL  SCIENCE 

as  the  boiling  point,  of  water.  It  has  this  advantage,  how- 
ever, that  zero  means  a  definite  thing  (namely,  the  freezing 
point),  and  that  one  hundred  is  an  easier  number  with  which 
to  deal  than  two  hundred  and  twelve.  In  foreign  countries, 
and  in  scientific  work  everywhere,  the  Centigrade  scale  is 
used,  and  no  doubt  it  will  gradually  supplant  the  Fahrenheit, 
even  for  common  purposes. 

References :  — 

1.    1803:129-134.  Thermometry. 

a.    1801 :  254.  Temperature. 

6.    1801 :  255-258.  Thermometers  and  Thermometer  Scales. 

c.  1804  :  251-252.  Definition  of  Temperature. 

d.  1804 :  254-257.  Graduation  of  Thermometers. 

e.  1805  :  292-296.  Temperature  and  Thermometers. 
/.    1806 :  310-313.  Temperature  and  Thermometers. 
g.    1807  :  163.  Temperature  Defined. 

h.    1808 :  206-207.      Temperature  Defined. 

Experiment  7.  —  The  Fixed  Points  of  the  Thermometer. 

Apparatus :  A  thermometer  with  scale  — 10°  to  225° 
Fahrenheit,  a  Centigrade  thermometer  with  scale  —  20°  to 
110°,  two  beakers  100  c.c.,  ring  stand,  asbestos  mat,  5"X5", 
lamp  for  heating. 

Materials :  Crushed  ice,  water,  matches. 

a.  Put  both  thermometers  in  the  beaker  which  contains  the 
ice,  and  allow  them  to  remain  until  the  mercury  ceases  to  fall. 
What  do  the  thermometers  indicate  ?  What  is  the  difference 
between  0°  C.  and  32°  F.? 

6.  Put  both  thermometers  in  some  cool  water  and  heat 
the  beaker  over  an  asbestos  mat.  Read  the  thermometers 
when  boiling  begins.  Which  is  hotter,  the  Fahrenheit  ther- 
mometer or  the  Centigrade  thermometer  ? 


CONDUCTION  23 

17.    CONDUCTION 

Heat  is  conveyed  from  one  body  to  another,  or  from  one 
part  of  the  same  body  to  another  part,  by  means  of  the  mole- 
cules jostling  against  one  another.  If  we  heat  one  end  of  a 
piece  of  copper  wire,  the  other  end  soon  becomes  hot,  because 
the  more  rapidly  moving  molecules  hit  against  their  neigh- 
bors. Not  only  do  solids  conduct  heat,  but  liquids  and  gases 
may  convey  heat  in  this  method,  although  not  as  readily. 
Materials  which  conduct  heat  are  called  conductors.  There 
are  good  conductors  and  poor  conductors. 

This  explains  why  metals  and  stone  feel  colder  than  wood 
or  cloth  on  a  cold  day,  and  warmer  on  a  hot  day,  although 
all  of  the  objects  are  at  the  same  temperature.  In  the  pres- 
ence of  cold,  therefore,  good  conductors  will  feel  cold  in  com- 
parison to  some  given  body,  and  will  take  away  its  heat  more 
readily  than  will  poor  conductors.  Similarly,  in  the  presence 
of  heat,  they  will  feel  warmer  than  the  body,  and  give  up  their 
heat  to  it  readily. 

References :  — 

1.    1803:216-219.  Conduction. 

a.    1801 :  286-288.  Conduction  and  Applications  of  Conduc- 
tion, 

fe.    1804:294-296.  Conduction. 

c.  1805:322-325.  Conduction. 

d.  1806:301-305.  Conduction. 

e.  1807  :  164-166.  Conduction. 
/.    1808:216-217.  Conduction. 

Experiment  8.  —  Conduction. 

Apparatus:    Burner,  glass  tube  6"  long,  copper  and  iron 
wires  No.  12,  6"  long,  test  tube  6"  X  I",  test-tube  holder, 
a.  Hold  one  end  each  of  the  glass  tube  and  of  the  copper 


24  INTRODUCTION  TO  GENERAL  SCIENCE 

and  iron  wires  in  the  flame.     Which  one  conducts  the  heat  to 
the  hand  first?    Which  one  last? 

b.  Fill  the  test  tube  nearly  full  of  water  and  place  it  in  the 
test-tube  holder.  Hold  the  tube  obliquely  so  that  the  flame  of 
the  burner  heats  the  top  of  the  Tvater,  but  does  not  touch  the 
glass  where  there  is  no  water.  When  the  water  boils  at  the  top, 
feel  the  bottom  of  the  tube.  Is  water  a  good  conductor  of  heat  ? 

18.    CONVECTION 

All  bodies  expand  when  heated,  whether  they  are  solids, 
liquids,  or  gases.  It  follows  that  a  given  weight  of  material 
occupies  more  space,  when  heated,  than  when  cold.  There- 
fore a  given  volume  of  a  hot  material  weighs  less  than  the 
same  volume  of  the  same  material  when  cold.  Thus,  if  there 
is  a  mixture  of  hot  air  and  cold  air,  or  hot  water  and  cold 
water,  the  colder,  heavier  material  will  push  up  the  warmer, 
lighter  material.  We  say  that  hot  air  rises;  it  is  more  cor- 
rect to  say  that  it  is  pushed  up  by  colder  air.  For  the  same 
reason  a  balloon  does  not  rise  of  itself,  but  is  pushed  up  by 
the  air,  which  is  heavier  than  the  contents  of  the  balloon. 

In  the  above-mentioned  method  of  heat  distribution,  the 
material  heated  keeps  turning  over  and  over.  Thus  it  is 
called  convection,  and  the  currents,  which  are  produced,  are 
called  convective  currents.  Upon  convection  are  based 
methods  of  hot-air  heating,  and  hot-water  heating  of  houses, 
ventilation,  and  domestic  hot-water  boilers.  These  are  de- 
scribed in  the  next  section.  The  winds,  which  are  caused  by 
convective  currents  on  an  enormous  scale,  are  treated  in 
Section  94,  Winds. 
References :  — 

1.    1803  :  219-221.  Convection  of  Liquids, 

a.    1801:288-290.      Convection  in  Water. 


CONVECTION  25 

6.    3802:286.  Convection. 

c.  1804:296-298.  Convection. 

d.  1805:325-326.  Convection. 

e.  1806:305-306.  Convection. 
/.    1807:166-167.  Convection. 

g.    1808  :  217.  Convection  in  Gases. 

h.    1809  :  160.  Convection. 

Experiment  9.  —  Convection  in  Gases. 
Apparatus:    Chalk  box  and  cover,  piece  of  window  glass 
to  fit  as  a  sliding  cover  in  chalk  box. 

Materials:  Candle  not  over  2"  long,  matches,  touch  paper.* 

a.  Cut  a  hole  one  inch  square  in  one  side  of  the  box  close 
to  one  end  and  another  hole  in  the  same  side  of  the  box,  but 
close  to  the  other  end.   Opposite  this  latter  hole'cut  a  third,  in 
the  other  side  of  the  box.     Place  the  box  on  the  table  with  the 
end  having  two  holes  near  it  at  the  top.     Light  a  candle  and 
place  it  near  the  bottom  hole.   Take  the  wooden  cover  of  the 
box  and  make  a  partition  of  it,  dividing  the  box  lengthwise 
into  two  equal  parts.     In  this  partition,  cut  a  hole  near  the 
bottom.     Slide  the  glass  cover  in  place  and  apply  smoking 
touch  paper  near  the  lower  hole.     Where  does  the  smoke  go  ? 
Why? 

b.  Close  lower  hole  and  place  touch-paper  near  upper  hole 
of  other  side.     Describe  and  explain. 

Experiment  10.  —  Convection  in  Water. 
Apparatus :  Test  tube,  test-tube  holder,  lamp. 
Materials:  Sawdust. 

a.  Fill  a  test  tube  nearly  full  of  water  and  mix  in  it  a  very 
small  pinch  of  fine  sawdust.  Hold  the  test  tube  vertically 

*  To  make  touch-paper :  Soak  blotting  paper  in  a  water  solution  of  po- 
tassium nitrate  (saltpeter)  containing  all  of  the  potassium  nitrate  which  will 
dissolve.  Dry  and  cut  into  strips  j  inch  wide. 


26  INTRODUCTION  TO  GENERAL  SCIENCE 

over  the  flame  and  to  one  side  of  it  so  that  the  flame  will  heat 
one  side  of  the  water  only.  Tell  what  you  see,  and  explain. 
Why  is  sawdust  added  to  the  water  ? 

19.    VENTILATION  AND  HEATING  OF  BUILDINGS 

Nearly  every  application  of  knowedge  which  we  make  use 
of  in  business  or  for  our  comfort  is  founded  upon  some  of  the 
various  phenomena  of  nature.  In  the  last  experiments  we 
saw  how  easy  it  is  to  produce  currents  of  air  and  water  by 
means  of  heat,  while  at  the  same  time  the  heat  was  distributed. 
We  make  use  of  these  facts  in  the  ventilation  and  heating  of 
buildings. 

The  Hot-air  System.  Coal  or  wood  is  burned  in  a  fire  pot 
which  is  surrounded  by  an  air  space.  This  space  has  one 
inlet  for  cold  and  fresh  outdoor  air,  and  several  outlets,  each 
of  which  leads  to  some  room  of  the  house.  The  air  around 
the  fire  pot  becomes  hot,  and  therefore  expands,  and  is  lighter 
per  given  volume.  This  is  pushed  out  of  the  heating  space  by 
the  outside  cold  and  heavier  air  coming  in.  Thus  the  rooms 
of  the  house  are  supplied  with  a  continuous  stream  of  warm, 
fresh  air.  This  system  ventilates  as  well  as  warms  the  whole 
building.  Its  great  disadvantage  is  that  the  windy  side  of 
the  building  does  not  receive  its  share  of  the  heat.  In  order  to 
overcome  this  fault,  power-driven  fans  are  placed  near  the 
furnace,  and  the  warm  air  is  forced  to  go  where  it  is  required. 

The  Hot-water  System.  In  this  system  the  fire  box  is  partly 
made  of  coils  of  iron  pipes  which  contain  water.  The  ambi- 
tion of  the  builder  is  to  have  all  of  the  heat  of  the  fire  given  to 
the  water.  The  water,  when  warm,  expands,  is  lighter  than 
the  colder  water,  and  circulates  around  the  pipe  system  of 
the  whole  house.  The  rooms  are  supplied  with  coils  of  pipes, 


RADIATION  OF  HEAT  27 

called  radiators,  which  are  intended  to  give  large  surface  so 
that  the  heat  of  the  water  may  be  readily  given  up  to  the  air 
of  the  room.  It  will  be  noted  that  no  fresh  air  is  supplied  by 
this  method  of  heating,  and  therefore  some  ventilation  is 
necessary.  The  advantage  of  this  system  is  that  all  of  the 
house  may  be  evenly  heated  whether  the  wind  blows  or  not. 
See  Section  190,  Dangers  of  Vitiated  Air. 

Heating  by  means  of  steam  will  be  explained  in  Section  25, 
Evaporation  and  Condensation. 

References :  — 

1.  1710  :  33-45.  Heating  and  Ventilation. 

2.  1803  :  223-225.  Heating  and  Ventilation. 
a.    1801 :  290.  Ventilation. 

6.  1804:298-302.  Ventilation. 

c.  1805  :  326.  Ventilation. 

d.  1808  :  218.  Ventilatkm. 

e.  1809  :  161.  Ventilation. 

20.    RADIATION  OF  HEAT 

Heat  is  also  radiated ;  that  is,  it  passes  off  in  straight  lines 
from  one  body  to  all  other  bodies.  In  some  way  the  swiftly 
moving  molecules  have  the  power  to  give  out  energy  very 
similar  to,  though  much  weaker  than,  the  energy  we  receive 
from  the  sun.  Radiated  heat  is  very  noticeable  if  we  are  in 
front  of  an  open  fireplace,  for  the  radiation  there  is  caused 
only  from  the  action  of  molecules.  The  energy  from  the  sun 
may  be  condensed  by  means  of  a  lens  or  "  burning  glass  " 
and  so  high  a  temperature  obtained  as  to  set  fire  to  paper, 
cloth,  and  even  wood  and  coal. 

Material  which  is  black  and  rough  is  the  best  radiator; 
that  which  is  smooth  and  shiny  makes  a  very  poor  radiator, — 
therefore  if  we  wish  to  keep  anything  hot,  we  should  place  it 


28  INTRODUCTION  TO  GENERAL  SCIENCE 

in  a  very  smooth,  highly  polished  dish.  Thus  coffee,  in  a 
brightly  polished  pot,  keeps  warm  longer  than  in  a  darker, 
rougher  dish. 

References :  — 

1.  1002  :  390.  The  Energy  Radiated  by  the  Sun. 

2.  1803  :  221-222.  Nature  of  Radiation. 
a.    1001 :  150-151.  Solar  Radiation. 

6.  1004 :  166.  Radiation  from  the  Sun's  Surface. 

c.  1801 :  291-292.  Radiation  of  Heat. 

d.  1802:286-288.  Radiation. 

e.  1804:303.  Radiation. 

/.  1804 :  416-421.  Thermal  Effects  of  Radiation. 

g.  1805  :  327-328.  Radiation  of  Heat. 

h.  1806:306-307.  Radiation. 

i.  1807 : 167-170.  Radiation  of  Heat. 

j.  1808 :  218-221.  Radiation  of  Heat. 

Experiment  n.  —  Radiation  of  Heat. 

Apparatus :  Two  baking  powder  or  spice  cans,  with  labels 
removed,  thermometer,  alcohol  lamp  filled  with  turpentine 
(one  for  the  class  is  enough). 

a.  Polish  the  outside  of  one  can,  and  smoke  the  outside  of 
the  other  can.  Fill  both  with  boiling  water  and  place  them 
in  the  shade  and  out  of  a  draft.  At  the  end  of  ten  minutes 
take  the  temperature  of  each.  State  results  and  explain. 
Repeat  at  the  end  of  ten  minutes  more. 

21.    ABSORPTION  OF  HEAT 

The  only  kind  of  heat  which  is  said  to  be  absorbed  is  radiant 
heat,  or  the  heat  of  radiation.  Absorption  of  this  radiant  heat 
is  not  very  noticeable  except  in  the  case  of  heat  which  is  re- 
ceived from  the  sun.  A  good  radiator  is  a  good  absorber. 
Thus  black  and  rough  clothing  is  warmer  than  white,  if  the 


ABSORPTION  OF  HEAT  29 

person  is  to  be  in  the  sunshine.  For  the  same  reason,  dark- 
colored  earth  absorbs  more  heat  than  the  lighter-colored  soil, 
which  may  be  desirable  when  heat  is  needed  for  crops. 

If  materials  were  transparent,  they  would  not  absorb  any 
heat.  There  is,  however,  no  substance  that  is  truly  transpar- 
ent, and  so  there  is  always  some  absorption.  The  atmosphere 
absorbs  about  forty  per  cent  of  the  sun's  heat  which  reaches 
it,  and  dirty  water  absorbs  practically  all  of  the  heat  within  a 
few  inches  of  its  surface.  If  we  sit  by  a  window,  in  the  sun- 
shine, we  may  be  warmed  by  the  energy  from  the  sun,  although 
the  window  glass,  through  which  the  energy  passes,  is  not 
noticeably  heated.  Therefore  radiant  "  heat  "  is  really  not 
heat,  but  a  form  of  energy  which  may  be  changed  into  heat. 

An  application  of  absorption  of  heat  is  the  solar  heater  for 
water.  This  consists  of  a  large  number  of  pipes  arranged  in  a 
glass-covered  box,  which  is  usually  placed  upon  the  roof  of  the 
house.  The  water  must  pass  through  all  of  the  pipes  before 
it  can  reach  the  outlet.  The  interior  of  the  box  and  also  the 
pipes  are  painted  black,  without  any  gloss,  and  the  water 
absorbs  enough  heat  to  be  sufficiently  warm  for  washing 
dishes  and  for  other  domestic  purposes.  Why  is  the  box 
covered  with  glass? 

References :  — 

1.  1103  :  27-28.  Absorption  of  Heat- by  the  Atmosphere. 

2.  1803  :  464-465.          Radiation  and  Absorption. 

a.  1801 :  292-295.  Absorption  —  Selective  Absorption. 

6.  1802  :  324.  Effect  of  Absorption. 

c.  1804  :  422.  Good  Radiators,  Good  Absorbers. 

d.  1805:328-331.  Absorption  —  Selective  Absorption. 

e.  1806 :  392.  Absorbing  Power. 

/.    1807  : 170-172.     Reflection  and  Absorption  at  Surfaces. 
g.    1808  :  221-223.     Radiating  and  Absorbing  Powers. 
h.    1810:177.  Absorption  of  Radiant  Energy. 


30  INTRODUCTION  TO  GENERAL  SCIENCE 

Experiment  12.  —  Absorption  of  Heat. 

Apparatus:    The  same  as  in  Experiment  11. 

a.  Put  equal  amounts  of  water  of  the  same  temperature 
into  the  two  cans,  and  expose  them  to  the  sunlight,  in  a  place 
which  is  sheltered  from  wind.  Leave  for  twenty  minutes  and 
then  test  the  temperature  of  each.  Which  is  warmer  ?  Did 
you  expect  this  ?  Nearly  all  of  the  "  laws  "  of  nature  work 
both  ways. 

Experiment  for  places  where  there  is  snow:  Place  squares 
of  different-colored  cloth,  including  white  and  black,  on  the 
surface  of  the  snow,  in  the  sunshine.  Some  will  absorb  more 
heat  than  others,  and  will  sink  deeper  into  the  snow.  Measure 
the  different  depths,  and  arrange  the  colors  in  a  table,  accord- 
ing to  the  amount  of  heat  which  they  have  absorbed  in  a 
given  time. 

22.    MEASUREMENT  OF  HEAT 

Section  16  treated  of  the  measurement  of  temperature,  but 
was  not  concerned  with  the  measurement  of  heat.  We  have 
learned  that  heat  is  due  to  the  motion  of  the  molecules.  Now 
the  temperature  of  a  body  indicates  the  average  velocity  of 
the  molecules,  while  the  quantity  of  heat  is  due  to  the  sum 
total  of  all  of  the  molecular  motion. 

The  unit  of  heat  measurement  is  the  calorie,  and  it  is  the 
amount  of  heat  which  is  necessary  to  raise  the  temperature 
of  one  gram  of  water  from  4°  to  5°  Centigrade.  (One  ounce  is 
equivalent  to  about  twenty-eight  grams.)*  This  is  the  unit 
which  is  used  in  all  scientific  work,  but  there  is  another  unit 
which  is  used  in  engineering.  This  is  called  the  British 
Thermal  Unit,  and  it  is  the  amount  of  heat  which  is  necessary 
to  raise  one  pound  of  water  one  degree  Fahrenheit. 

*  A  nickel  five-cent  piece  weighs  five  grams. 


HEAT  OF  CHANGE  OF  STATE  31 

A  large  amount  of  water,  at  a  moderate  temperature,  may 
contain  more  heat  than  a  smaller  amount  of  water  at  a  higher 
temperature. 

References :  — 

1.    1803  :  175.  Unit  of  Heat  —  The  Calorie. 

a.    1801 :  269-270.  Measurement  of  Heat. 

6.    1802  :  272.  Measurement  of  Heat. 

c.  1804:260-261.  Thermal  Units. 

d.  1805  :  316.  Measurement  of  Heat. 

e.  1806:341.  Measure  of  Heat. 
/.    1807 :  182.  The  Heat  Unit. 

fir.    1808  :  237.  The  Measurement  of  Heat. 

h.    1809  :  179.  The  Unit  of  Heat  —  The  Calorie. 

Experiment  13.  —  Quantity  of  Heat  Comparison. 
Apparatus:    Burner,   ring  stand,  asbestos    mat,  beakers, 
100  c.c.,  150  c.c.,  200  c.c.,  thermometer. 

a.  Boil  some  water  in  the  150  c.c.  beaker  and  have  50  c.c. 
of  water  in  the  100  c.c.  beaker,  and  150  c.c.  of  water  in  the 
200  c.c.  beaker,  both  of  the  same  temperature.     Completely 
fill  these  two  beakers  with  boiling  water,  thus  adding  50  c.c. 
to  50  c.c.,  and  50  c.c.  to  150  c.c.      Take  the  temperature  of 
each,    after    stirring.     Which   has  the  higher  temperature? 
What  is  the  relative  amount  of  change  in  degrees? 

b.  Since  the  same  amount  of  heat  was  added  in  each  case, 
draw  your  conclusions  in  regard  to  the  relation  between  heat 
and  temperature. 

23.    HEAT  OF  CHANGE  OF  STATE 

There  is  another  rather  peculiar  change,  caused  by  heat, 
which  is  called  change  of  state.  By  this  is  meant  the  passing 
from  the  solid  to  the  liquid  form,  and  from  the  liquid  to  the 
gaseous.  A  liquid  contains  more  heat  energy  than  does  the 


32  INTRODUCTION  TO  GENERAL  SCIENCE 

same  material  in  a  solid  state,  while  a  gas  contains  still  more 
heat  energy  than  does  the  same  weight  of  liquid.  The  tem- 
perature of  ice  cannot  be  raised  above  32°  Fahrenheit  until 
all  the  ice  is  melted.  The  heat  goes  to  give  the  molecules 
enough  energy  to  exist  in  the  form  of  a  liquid.  For  a  similar 
reason  water  cannot  -be  heated  in  the  open  air,  above  its 
boiling  point  —  212°  Fahrenheit.  The  heat  gives  the  water 
molecules  sufficient  energy  to  exist  in  the  gaseous  form.  Now, 
since  there  is  no  loss  in  nature,  this  same  amount  of  heat 
which  is  necessary  to  change  a  solid  into  a  liquid  is  given  out 
again,  when  the  liquid  changes  back  into  a  solid.  Farmers  in 
cold  countries  make  use  of  this  fact  by  placing  in  their 
cellars  large  tubs  of  water,  which,  as  it  freezes,  gives  out  to 
the  cellars  the  same  amount  of  heat  that  would  be  necessary 
to  melt  the  same  weight  of  ice  to  water.  Thus  Vegetables 
may  be  kept  from  freezing,  since  their  freezing  point  is 
slightly  lower  than  that  of  water.  Again,  the  heat  which  is 
necessary  to  change  water  into  steam  is  given  out  when  the 
steam  condenses  to  water  again.  Upon  this  is  based  the 
system  of  steam  heating.  The  water  which  leaves  the  steam 
radiator  has  just  as  high  a  temperature  as  the  steam  from 
which  it  was  condensed,  although  a  great  amount  of  heat 
has  been  given  off  by  the  condensation  of  the  steam.  See 
Section  25,  Applications  of  Evaporation  and  Condensation. 
References :  — 

1.  1803  :  196.  Definition  of  Heat  of  Fusion. 

2.  1803  :  198.  Latent  Heat  of  Fusion. 

3.  1803  :  203.  Definition  of  Heat  of  Vaporization. 

4.  1803  :  204.  Latent  Heat  of  Vaporization. 

a.  1801 :  274-278.  Heat  and  the  Change  of  State. 

b.  1802:304.  Solidification. 

c.  1804  :  278-287.  Fusion  and  Vaporization. 

d.  1805 :  333,  Heat  of  Fusion. 


HEAT  OF  CHANGE  OF  STATE  33 

e.  1805 :  339-341.  Heat  of  Vaporization. 

/.  1806  :  350.  Heat  of  Fusion. 

g.  1807  :  189-190.  Heat  of  Fusion. 

h.  1807  :  204-205.  Heat  of  Vaporization. 

i.  1808 :  239-240.  Latent  Heat  of  Fusion  and  of  Vaporization. 

j.  1809 :  184-185.  Heat  of  Fusion. 

k.  1809  :  194.  Heat  of  Vaporization. 

Experiment  14.  —  Heat  of  Vaporization  and  of  Fusion. 

Apparatus :  Burner,  ring  stand,  asbestos  mat,  3"  evaporat- 
ing dish,  thermometer. 

Materials :  Ice. 

a.  Put  about  5  c.c.,  of  ice  water  in  the  evaporating  dish 
and  see  how  many  minutes  it  takes  to  bring  it  just  to  a  boil. 
Then,  keeping  the  burner  in  the  same  position  and  condition, 
see  how  many  minutes  it  takes  to  boil  away  the  water.  How 
many  calories  did  it  take  to  raise  the  temperature  of  5  c.c. 
( =  5  grams)  of  water  from  0°  Centigrade  to  100°  Centigrade  ? 
Since  the  amount  of  heat  which  is  received  from  a  burner  is 
nearly  constant,  about  how  many  calories  did  it  take  to  boil 
away  the  liquid ;  that  is,  how  much  did  it  take  to  change  5  c.c. 
of  water  at  100°  C.  into  steam  at  100°  C.?  Then  how  much 
did  it  take  for  one  gram  of  water  ? 

6.  Put  5  g.  of  ice  in  the  evaporating  dish,  place  it  on  the 
mat,  over  the  burner,  and  see  how  many  minutes  elapse  before 
it  is  melted.  Then  continue  to  heat  the  -water  for  the  same 
number  of  minutes.  At  the  end  of  this  time  note  the  tem- 
perature of  the  water.  How  many  calories  of  heat  were  re- 
quired to  change  5  g.  of  water  from  0°  C.  to  the  final  tempera- 
ture ?  Then  how  many  calories  for  1  g.  of  water  ?  Since  the 
heat  which  was  received  from  the  burner  may  be  considered  as 
being  constant,  how  many  calories  were  needed  to  melt  1  g.  of 
ice  ?  Compare  your  results  with  any  of  the  reference  books, 


34  INTRODUCTION  TO  GENERAL  SCIENCE 


24.    EVAPORATION  REQUIRES  HEAT 

We  saw  in  Experiment  14  that  heat  is  required  to  change  a 
liquid  into  a  gas,  at  least  in  the  case  of  boiling.  Yet  water 
evaporates,  or  changes  from  the  liquid  form  to  the  vapor  form, 
at  all  temperatures.  For  instance,  the  clothes  dry  on  the 
line,  on  wash  day,  although  the  temperature  of  the  air  is  far 
below  the  boiling  point.  It  can  be  shown  that  even  ice  may 
evaporate  without  first  melting,  that  is,  ice  may  change  from 
the  solid  state  directly  into  the  vapor  state  and  not  pass 
through  the  liquid  state. 

Although  it  is  not  always  evident,  yet  every  molecule  of  a 
liquid  which  leaves  the  liquid  and  becomes  part  of  a  gas  or 
vapor  requires  heat  in  order  to  make  the  change.  This  heat 
comes  from  the  liquid,  which  receives  its  heat  from  its  sur- 
roundings. Otherwise  the  temperature  falls,  and  the  liquid 
becomes  cooler. 

Evaporation  of  any  liquid  lowers  the  temperature.  Thus 
the  evaporation  from  the  surface  of  the  body  tends  to  lower 
the  temperature  of  the  body.  At  all  times,  whether  we  are 
warm  or  cold,  we  are  perspiring,  but  evaporation  takes  place 
just  as  fast  as  the  perspiration  exudes,  and  we  do  not  have  the 
sensation  of  dampness. 

A  healthy  person  perspires  an  amount  between  a  pint  and 
a  quart  every  twenty-four  hours.  A  man  violently  exercising 
may  perspire  over  four  quarts  ±u  a  day. 

A  current  of  air  removes  the  water  vapor  and  permits  a 
more  rapid  evaporation  of  the  remaining  liquid.  Therefore 
a  person  is  cooler  in  a  draft  than  in  still  air,  and  is  liable  to 
reduce  his  external  temperature  too  rapidly  and  catch  cold,  if 
his  clothes  are  damp. 


APPLICATIONS  OF   EVAPORATION,  CONDENSATION    35 

References :  — 

1.  1503  :  397-398.          Regulation  of  Body  Temperature. 

2.  1803  :  100-101.          Cooling  Effects  of  Evaporation  Explained. 

3.  1803  :  210.  Intense  Cold  by  Evaporation. 

a.    1507 :  241-244.  Perspiration  as  a  Heat  Regulator. 

6.    1801 :  281.  Cold  by  Evaporation. 

c.  1804 :  289.  Heat  Consumed  in  Evaporation. 

d.  1805;  340.  Cold  by  Vaporization. 
e.'  1806 :  365-366.  Cooling  by  Evaporation. 

/.    1807 :  193.  Disappearance  of  Heat  during  Vaporiza- 

tion. 


25.    APPLICATIONS  OF  EVAPORATION  AND  CONDENSATION 

As  fast  as  man  really  understands  the  phenomena  of  nature, 
he  makes  use  of  them  for  his  own  comfort,  or  for  profit.  Ac- 
cordingly, life  means  most  to  the  one  who  knows  most,  and 
can  use  his  knowledge  in  his  daily  life.  Cooling  by  evapora- 
tion, and  the  reverse,  that  is,  warming  by  condensation,  are 
but  two  more  examples  of  the  application  of  knowledge  to 
practical  ends. 

The  saying  that  it  is  a  poor  rule  which  does  not  work  both 
ways  applies  more  strictly  to  science  than  to  anything  else. 
In  fact,  there  are  but  few  physical  or  chemical  changes  of  form 
or  energy  which  are  not  reversible.  Evaporation  requires 
heat ;  that  is,  heat  is  absorbed  by  the  material  which  is  evap- 
orating. When  this  vapor  is  condensed,  exactly  the  sama 
amount  of  heat  is  given  out.  There  is  no  loss  in  nature. 

If  water  is  placed  in  a  porous  earthen  jar,  the  water  which 
seeps  through  evaporates  into  the  air  and  cools  the  remainder. 
The  drier  the  air,  and  the  more  air  that  is  brought  into  con- 
tact with  the  surface  of  the  water,  the  lower  will  become  the 
temperature. 


36  INTRODUCTION  TO  GENERAL  SCIENCE 

Milk  may  be  kept  from  souring,  and  butter  may  be  pre- 
served in  a  more  solid  condition,  by  being  placed  in  a  saucer 
of  water  and  wrapped  with  a  cloth  which  is  kept  damp  by  the 
water  in  the  saucer.  Cooling  closets  are  constructed  on  the 
same  principle;  that  is,  a  light  framework  is  covered  with 
sacking  which  is  kept  moist  by  a  tank  on  top.  The  heat 
which  the  water  requires  in  order  to  become  a  vapor  is  taken 
from  the  food  within  the  closet,  and  thus  the  food  becomes 
cooled. 

Those  liquids  which  have  the  tendency  to  evaporate  easily 
necessarily  lower  the  temperature  of  their  surroundings  more 
than  does  water  when  it  evaporates.  Ether,  alcohol,  and 
any  of  the  volatile  liquids  do  this  to  a  very  marked  degree. 
It  is  quite  easy  to  freeze  water  by  means  of  the  evaporation  of 
ether. 

The  liberation  of  heat  by  condensation  is  made  use  of  in 
the  system  of  steam  heating.  Water  is  boiled  in  a  boiler,  and 
a  large  amount  of  heat  is  absorbed  in  changing  the  water  to 
steam.  The  steam  passes  through  pipes  to  the  colder  parts 
of  a  building  and  condenses  to  water,  thereby  giving  up  to  the 
air  of  the  rooms  all  of  the  heat  which  it  had  absorbed  from 
the  fire.  The  water  which  leaves  a  radiator  may  be  of  the 
same  temperature  as  the  steam  which  entered,  although  it 
has  given  up  a  vast  amount  of  heat  in  its  condensation.  Dew, 
in  forming,  raises  the  temperature  of  the  atmosphere,  and  a 
foggy  night  is  usually  warmer  than  a  clear  night.  Both  these 
facts  are  due  to  the  principles  of  condensation  already  ex- 
plained. 
References:  — 

1.  1103 : 134-135.          Formation  of  Ground  Fog  Prevents  Fur- 

ther Cooling. 

2.  1803  :  102.  Freezing  by  Evaporation. 


APPLICATIONS  OF  EVAPORATION,  CONDENSATION    37 

3.    1803:212-214.  Liquid  Air  — Manufactured  Ice. 

a.    1802 :  317.  Plan  of  an  Ice  Plant. 

6.    1805  :  351-354.  Cold  by  Expansion  — Ice. 

c.  1806 :  370-372.  Steam  Heating  of  Buildings. 

d.  1807  :  206-207.  Cooling  by  Evaporation  —  Applications. 

e.  1809  :  194-195.  Ice  Machines. 

Experiment   15.  —  Cooling  by  Evaporation. 
Apparatus :   Beaker  50  c.c.,  test  tube  6"  X  f",  syringe  bulb 
with  rubber  outlet  tube,  glass  tube  i"  diameter,  6"  long. 
Materials:  Ether,  alcohol. 

a.  Pour  a  little  alcohol  on  the  hand,  and  wave  it.     Repeat, 
using  ether.     What  is  the  difference  ?     Why  ? 

b.  Put  20  c.c.  ether  in  the  beaker,  and  place  in  it  the  test 
tube  containing  not  more  than  2  c.c.  cold  water;  gently  force 
air  through  the  ether  by  means  of  the  bulb,  using  the  glass  tube 
in  the  ether.     The  water  should  freeze  in  about  ten  minutes. 

Experiment  16. — Heating  by  Condensation. 

Apparatus:  Burner,  ring  stand,  asbestos  mat,  flask  250  c.c., 
single-hole  rubber  stopper  to  fit  flask,  glass  tube  J"  diameter, 
water  trap,  rubber  tube  in  short  pieces  to  join  glass  tubing, 
beaker  150  c.c.,  thermometer. 

a.  Boil  water  in  the  flask  and  pass  the  steam,  by  means  of 
the  glass  and  rubber  tubing,  through  the  water  trap,  into 
100  c.c.  water  which  has  a  temperature  of  41°  C.,  until  the 
temperature  becomes  95°  C.  Measure  the  water  in  the 
beaker.  How  many  grams  of  water  were  condensed  ?  To 
raise  100  c.c.  of  water  from  41°  C.  to  95°  C.  required  how  many 
calories  ?  Divide  this  number  by  the  number  of  grams  of 
water  which  were  condensed,  and  you  will  obtain  the  number 
of  calories  which  each  gram  of  steam  gave  up  while  condens- 
ing. What  results  did  you  obtain  ?  How  does  this  compare 
with  your  references? 


38  INTRODUCTION  TO  GENERAL  SCIENCE 

26.    THE  STEAM  ENGINE 

Another  application  of  the  laws  of  nature  is  instanced  in 
the  case  of  the  steam  engine.  When  a  liquid  evaporates,  the 
average  velocity  of  its  molecules  is  much  greater  than  that 
which  they  had  in  liquid  form.  When  these  rapidly  moving 
molecules  strike  the  walls  of  any  container  which  restrains 
them  from  unlimited  motion,  they  exert  a  pressure  upon  the 
walls  that  is  proportional  to  their  velocity.  The  latter  in- 
creases with  the  temperature.  When  water  is  boiled,  evap- 
oration takes  place  rapidly,  and  the  steam  may  also  be 
heated  far  above  the  boiling  point.  Therefore  we  can  obtain 
any  pressure  we  may  desire. 

The  steam  so  generated  is  conducted  alternately,  by  means 
of  automatic  valves,  to  the  opposite  sides  of  a  moving  piston 
which  slides  in  a  cylinder.  The  references  give  complete 
details  concerning  various  kinds  of  steam  engines. 

References :  — - 

1.    1803:186-191.  The  Steam  Engine. 

a.    1801 :  297-299.  The  Steam  Engine. 

6.    1804:  308-313.  The  Steam  Engine  and  the  Locomotive. 

c.  1805  :  312-314.  The  Steam  Engine. 

d.  1806:381-386.  The  Steam  Engine. 

e.  1807:212-213.  The  Steam  Engine. 
/.    1808 :  245-247.  The  Steam  Engine. 
g.    1809:203-207.  The  Steam -Engine. 
h.    1810 :  190-193.  The  Steam  Engine. 

27.    DISTILLATION  OF  LIQUIDS 

There  is  very  little  water  which  does  not  contain  some 
solid  dissolved  in  it.  It  may  be  purified,  however,  both  by 
natural  and  by  artificial  methods.  The  evaporation  from  the 


DISTILLATION  OF  LIQUIDS  39 

ocean,  and  other  large  bodies  of  water,  is  nature's  great  pro- 
cess of  distillation.  Rain  water,  falling  after  a  long  period  of 
rain,  is  practically  pure.  Waterfalls  and  rapids  cause  the 
oxygen  of  the  air  to  mingle  with  the  water  and  remove  the 
impurities  by  a  process  of  combustion.  Man  purifies  water 
by  boiling  it  and  condensing  the  steam.  If  water  boils 
slowly,  nothing  but  pure  water  passes  off,  except  dissolved 
gases  and  any  liquid  which  has  a  lower  boiling  point  than 
water,  all  the  solid  impurities  being  left  behind.  If  the  steam 
is  condensed,  we  have  what  is  called  distilled  water,  and  it 
tastes  very  flat,  as  it  has  no  air  dissolved  in  it.  Any  material 
which  can  be  readily  changed  from  a  liquid  to  a  vapor  may 
be  distilled.  Natural,  sparkling  water  has  quantities  of  air, 
and  sometimes  carbon  dioxide,  dissolved  in  it. 

References:  — 

1.  1703  :  45-47.  Distillation  of  Water. 

2.  1803  :  210-211.  Distillation  of  Water, 
a.    1701:50-51.  Distillation. 

I.  1702 :  56-57.  Distillation  of  Water. 

c.  1704  :  28-29.  Distillation  of  Water. 

d.  1704 :  211.  Distillation  of  Alcohol. 

e.  1706  :  39-40.  Distillation  of  Water. 
/.  1707  :  69-70.  Distillation  of  Water. 
g.  1708:30.  Distillation. 

Experiment  17.  — Distillation. 

Apparatus:  Ring  stand,  burner,  asbestos  mat,  flask  250c.c., 
rubber  stopper  with  one  hole,  glass  tubing  J'7  diameter,  rubber, 
tubing,  to  make  connections,  test  tube  6"  X  f  ",  beaker  150  c.c. 

Materials :  Table  salt,  molasses,  yeast. 

a.  Fill  flask  one  half  full  of  salty  water,  which  is  dirty 
(a  small  amount  of  mud  may  be  placed  in  the  water),  insert 
stopper,  fitted  with  glass  tube,  connect  by  means  of  the  rubber 


40  INTRODUCTION  TO  GENERAL  SCIENCE 

tubing  with  another  glass  tube  placed  in  a  test  tube,  and  place 
the  test  tube  in  the  beaker  half  full  of  cold  water.  Boil  the 
water  in  the  flask  only  so  fast  that  no  steam  will  come  from 
the  top  of  the  open  test  tube.  Compare  the  condensed  water 
with  the  water  which  is  in  the  flask.  Taste  a  little  and  state 
how  it  seems.  Place  your  thumb  over  the  top  of  the  test 
tube  and  shake  the  distilled  water  for  a  short  time.  Taste 
again  and  explain  the  results. 

b.  Mix  a  tablespoonful  of  molasses  with  a  pint  of  water  and 
half  a  yeast  cake,  and  allow  fermentation  to  take  place  for  two 
days.  Use  the  resulting  mixture  in  the  place  of  the  dirty  salt 
water,  but  heat  more  gently.  As  soon  as  you  obtain  a  few 
drops  of  distilled  liquid,  pour  it  out  on  the  flat  base  of  a  ring 
stand  and  touch  a  match  to  it.  What  happens  ?  What  is  it  ? 

28.    DESTRUCTIVE  DISTILLATION 

In  the  preceding  parargaph  we  considered  simple  distilla- 
tion, in  which  the  material  was  not  changed  but  merely  sepa- 
rated physically.  It  is  possible,  however,  to  carry  distillation 
so  far  that  the  substance  heated  is  broken  up  chemically,  and 
the  resulting  products  may  be  entirely  different  from  the 
original  substance.  This  is  called  destructive  distillation, 
and  the  products  obtained  by  this  process  are  often  very 
valuable. 

The  destructive  distillation  of  soft  coal  gives  gas,  coal  tar, 
coke,  carbon,  and  other  by-products.  Wood  yields  a  gas, 
wood  tar,  acetic  acid,  and  wood  alcohol.  Petroleum  yields 
several  volatile  liquids,  such  as  gasoline,  naphtha,  benzine, 
and  kerosene.  The  solid  remainder  is  paraffin  in  some  petro- 
leums and  asphalt  in  others.  See  Section  137,  Coal,  Soft  and 
Hard,  and  Section  138,  Petroleum  and  Natural  Gas. 


DESTRUCTIVE   DISTILLATION  41 

References :  — 

1.  1703 : 189-190.  Destructive  DistiUation  of  Wood. 

2.  1710 :  53-54.  Illuminating  Gas  from  Soft  Coal. 

3.  Circular  114.  Forest  Service,  U.  S.  Dept.  of  Agriculture, 
a.    1704  :  1G8-169.  Destructive  Distillation. 

6.  1706 :  188-189.  Formation  of  Charcoal  and  Coke. 

c.  1708 :  82-83.  Carbon  from  Other  Compounds. 

d.  1709  :  374-377.  Destructive  Distillation. 

e.  1712:255.  Destructive  Distillation. 

Experiment  18.  —  Destructive  Distillation. 

Apparatus:  Burner,  test  tube  6"xf",  test-tube  holder, 
ordinary  clay  pipe. 

Materials :   Chips  of  wood,  soft  coal,  rice,  sugar,  starch. 

a.  Place  a  few  chips  of  wood  in  a  test  tube  and  heat  it 
gently.  Notice  what  collects  on  the  upper  part  of  the  tube. 
Where  did  it  come  from  ?  Heat  more  strongly,  moving  the 
tube  through  the  flame  so  as  to  heat  it  uniformly.  As  soon 
as  the  smoke  becomes  quite  dense,  light  it.  What  does  a 
flame  indicate  always  ?  Continue  to  heat  the  wood,  until  no 
more  smoke  comes  off,  and  then  examine  the  residue.  What 
is  it? 

6.  Repeat  with  rice,  sugar,  and  starch.  (Different  pupils 
may  use  different  materials  and  compare  notes,  in  order  to 
save  time  and  material.)  What  are  your  conclusions  in  re- 
gard to  all  of  the  substances  which  have  been  heated  ? 

c.  Place  a  few  very  small  pieces  of  soft  coal  in  the  bowl  of 
a  clay  pipe,  cover  with  wet  clay  (mud  will  do)  and  heat 
strongly.  The  gas  will  burn  at  the  mouthpiece  for  a  con- 
siderable time.  After  the  gas  ceases  to  be  evolved,  examine 
the  residue.  Try  to  burn  the  residue.  Remembering  Para- 
graph (e)  in  Experiment  3,  draw  your  conclusions. 


42  INTRODUCTION  TO  GENERAL  SCIENCE 


29.    COOKING 

There  is  one  other  effect  of  heat  which  civilized  man  em- 
ploys, and  which  is  a  strong  civilizing  influence :  heat  changes 
food  so  as  to  render  it  more  soluble  in  the  digestive  juices, 
and  at  the  same  time  kills  all  microbes  in  the  food,  thus  pre- 
venting disease  from  entering  the  system.  Cooking,  which 
is  the  result  of  the  application  of  heat  to  food,  falls  under 
two  general  headings  —  boiling  and  baking.  Boiling  has  the 
advantage  of  constant  temperature,  which  is,  ordinarily,  212° 
Fahrenheit.  Fast  boiling  is  not  hotter  than  slow  boiling,  if 
the  dish  is  uncovered.  Covering  a  dish  raises  the  tempera- 
ture of  the  boiling  water,  since  the  cover  prevents  rapid 
radiation  of  heat. 

Roasting  or  baking  takes  place  at  varying  temperatures, 
according  to  the  kind  of  food  which  is  being  cooked.  It  is  to 
be  remembered  that  it  is  the  temperature  which  does  the 
cooking,  or,  to  put  it  another  way,  the  chemical  changes  which 
are  called  cooking  take  place  at  a  certain  temperature  for 
a  given  kind  of  food.  Therefore,  if  we  can  only  keep  food 
hot,  without  a  fire,  that  food  will  be  cooked  just  as  well  as  it 
would  be  in  a  stove.  This  is  the  principle  of  the  so-called 
fireless  cooker.  After  the  food  to  be  cooked  has  been  heated 
to  the  boiling  point,  we  place  it  in  receptacles  surrounded  by 
nonconductors  of  heat;  thus  the  heat  which  is  already  in  the 
material  stays  there,  and  chemical  changes  take  place  which 
result  in  cooking.  It  is  not  necessary  to  have  elaborate 
fireless  cookers.  Boxes  well  packed  with  excelsior,  or  felt 
from  a  hat  manufactory,  and  provided  with  a  tight-fitting 
cover,  also  well  packed,  will  serve. 

Here  are  a  few  of  the  principles  of  cooking  :  — 


COOKING  43 

1.  If  meat  is  to  be  cooked  for  a  stew,  the  pieces  should  be 
cut  small  and  put  in  cold  water  over  a  slow  fire.     This  allows 
the  juice  to  come  out.     Salting  the  water  will  increase  the 
flow  of  the  juice  and  make  the  meat  more  tender,  since  the 
addition  of  salt  raises  the  boiling  point  of  water. 

2.  If  the  cooking  water  is  to  be  thrown  away,  the  meat 
should  not  be  put  in  until  the  water  is  boiling  very  rapidly. 
If  the  meat  is  in  a  large  piece,  it  should  be  seared  all  over  in  a 
smoking-hot  pan  before  boiling.     This  keeps  in  the  juice. 

3.  To  prepare  a  roast,  the  oven  should  be  very  hot  at  the 
beginning  and  a  little  cooler^ after  the  first  half  hour.     The 
intense  heat  sears  the  outside  of  the  meat,  as  in  the  case  above. 

4.  In  frying  meat,  the  frying  pan  should  be  very  hot  at  first 
and  then  cooler  after  both  sides  of  the  meat  have  been  seared. 

5.  Bread  requires  the  hottest  possible  oven;  pies  should  be 
baked  in  an  oven  which  is  a  little  cooler,  while  cakes,  as  a  rule, 
do  not  need  a  very  hot  oven.     When  cakes  break  open,  it  is 
because  the  oven  is  so  hot  that  the  outside  of  the  cake  bakes 
before  the  mass  has  time  to  rise. 

References :  — 

1.  1501 :  52-53.  Cooking  and  Ways  of  Cooking. 

2.  1702  :  383-387.          Chemical  Changes  in  the  Cooking  of  Food. 

3.  1710:  121.  Necessity  for  Cooking. 

4.  1803  :  204-205.          Boiling  Point  Defined. 

5.  1901 :  172-175.  Heat  Destroys  Bacteria. 

6.  Farmers'  Bulletin  No.  34  :  14-19.    The  Cooking  of  Meats. 

7.  Farmers'  Bulletin  No.  256  : 9-13.    General  Principles  Under- 

lying Vegetable  Cooking. 

a.  1505  :  114-1 15.     The  Five  Modes  of  Cooking. 

b.  1506:44-45.         Ways  of  Cooking. 

c.  1507  :  53-56.          Cooking  a  Safeguard. 

d.  1508:71-72.         Effects  of  Cooking. 

e.  1805  :  337-338.      Laws  of  Ebullition. 


44  INTRODUCTION  TO  GENERAL  SCIENCE 

EXPERIMENT  FOB  THE  HOME 

Temperature  Causes  Cooking 

a.  Place  an  egg  in  boiling  water  and  boil  it  for  exactly  four 
minutes.     Open  the  egg  immediately  after  removing  it  from 
the  water  and  note  its  texture. 

b.  Place  another  egg  in  one  pint  of  boiling  water  and  re- 
move from  the  source  of  heat.     Allow  egg  to  remain  in  the 
cooling  water  for  ten  minutes.     Open  egg  immediately  and 
compare  it  with  the  first  .egg.     How  much  water  would  be 
necessary  to  cook  eight  eggs  by  this  method  ?    Would  there 
be  any  difference  in  the  result  if  the  egg  had  been  in  an  ice- 
chest? 

Eggs  cooked  at  a  lower  temperature  are  not  only  pleasanter 
to  eat  than  eggs  boiled  rapidly,  but  they  are  also  more  digesti- 
ble; that  is,  the  consumer  obtains  more  nourishment  from  such 
an  egg  at  less  expenditure  of  digestive  energy. 

30.    CHEMICAL  AND  PHYSICAL  CHANGES 

Changes  within  the  molecule  which  alter  its  composition 
are  called  chemical  changes.  After  such  changes  the  material 
is  entirely  different  from  what  it  had  been,  and  is,  in  fact,  a 
new  substance.  Examples  of  chemical  change  are  the  souring 
of  milk,  decay  of  food,  rotting  of  wood,  formation  of  coal  from 
wood,  destructive  distillation,  the  bleaching  of  any  material, 
and  any  action  which  involves  a  permanent  change. 

Physical  changes  are  concerned  with  the  molecules  as  a 
whole,  and  are  limited  to  the  different  arrangement  of  the 
molecules,  or  their  relative  velocities.  Physical  changes  are 
often  temporary,  such  as  the  melting  of  ice  and  the  freezing 


CHEMICAL  AND  PHYSICAL  CHANGES  45 

or  boiling  of  water.  The  color  of  some  materials  is  altered 
by  heat  or  dampness,  but  returns  to  its  original  tint  or  shade 
when  the  temperature  is  lowered  or  the  dampness  driven  off. 

References :  — 

1.    1703  :  2-4.  Relation  between  Chemistry  and  Physics, 

a.    1701 :  2-3.  Chemical  and  Physical  Changes. 

6.    1702  :  1-3.  Physical  and  Chemical  Changes. 

c.  1704  :  7-8.  Chemical  and  Physical  Changes. 

d.  1705  :  3-5.  Physical  and  Chemical  Changes. 

e.  1706 :  1-2.  Physical  and  Chemical  Changes. 
/.    1707  :  2-3.  Chemical  and  Physical  Changes. 
g.    1708 :  2.  Physical  and  Chemical  Changes. 
h.    1709  : 1-2.  Physical  and  Chemical  Changes. 
i.    1711 :  23-27.  Physical  and  Chemical  Changes. 
j.    1712 :  13-14.  Physical  and  Chemical  Changes. 

Experiment  19.  —  Physical  and  Chemical  Changes. 
Apparatus :   Burner,  tweezers,  test  tube,  6"  X  J",  test-tube 
holder. 

Materials:   Mercuric  oxide,  strips  of  copper  6"x|". 

a.  Barely  cover  the  bottom  of  a  test  tube  with  mercuric 
oxide,  and  heat  gently.     Note  change  in  color.    What  is  it  an 
example  of  ?    Let  the  test  tube  cool  a  little  and  see  if  what  you 
expect  happens. 

b.  Heat  the  test  tube  strongly  for  several  minutes  and  tell 
what  happens  to  the  mercuric  oxide.     The  material  on  the 
sides  of  the  test  tube  is  mercury.     Examine  it.     Mercuric 
oxide  is  a  compound  of  mercury  and  oxygen.     Where  is  the 
oxygen?    What  kind  of  a  change  has  taken  place? 

c.  Heat  one  end  of  the  copper  strip  until  the  other  end  is  too 
hot  to  hold  in  the  hand.     Let  it  cool.     Is  this  a  chemical 
change  or  physical  change  ? 

d.  Hold  one  end  of  the  copper  strip  by  the  tweezers  and  put 


46  INTRODUCTION  TO  GENERAL   SCIENCE 

the  other  end  in  the  flame.     Heat  for  ten  minutes  or  more 
Watch  the  color  of  the  copper  strip.     Examine  the  heated  end 
after  ten  minutes.    Bend  this  end  back  and  forth,  and  explain 
what  you  notice.     Give  it  a  name.     What  makes  you  think  so? 

31.    CHEMICAL  COMBINATION  PRODUCES  HEAT 

One  form  of  chemical  action  was  studied  in  Section  4, 
Combustion.  There  we  learned  that  the  union  of  oxygen  and 
some  combustible  produces  a  large  amount  of  heat.  From 
the  little  you  have  studied  of  general  science,  you  would 
expect  that  any  chemical  union  would  produce  heat.  This 
is  true  in  all  cases  where  there  can  be  no  further  chemical 
change.  The  heat  is  not  always  apparent  nor  of  the  same 
quantity  as  in  the  oxidation  of  substances,  but  it  is  quite 
noticeable  in  several  instances. 

Sulphuric  acid  and  water  when  poured  together  form  a 
chemical  union  which  liberates  a  large  quantity  of  heat. 
Balloonists  make  use  of  this  method  of  obtaining  heat  without 
a  fire,  which  would  be  dangerous.  Many  of  the  common 
metals  and  acids  combine  and  liberate  heat.  A  gas,  hydrogen, 
is  also  set  free.  This  gas  will  be  studied  in  Section  114, 
Composition  of  Water. 

References :  — 

1.    1703  :  220.  Heat  of  Formation  and  Decomposition. 

a.  1701 :  75-76.  Heat  of  Reaction. 

b.  1704 :  318-319.  Thermal  Relations  of  Chemical  Changes. 

c.  1705  :  147-150.  Heat  of  Chemical  Changes. 

d.  1706:112-113.  Heat  and  Chemical  Action. 

e.  1708:117-118.  Heat  of  Chemical  Action. 
/.    1709 :  218-219.  Heat  of  Formation. 


FRICTION  AND  COMPRESSION  PRODUCE  HEAT    47 

EXPERIMENTS  FOR  THE  TEACHER 

Use  a  thermometer  with  large  index,  and  show  the  high 
temperature  produced  by  pouring  sulphuric  acid  into  water 
(use  care) ;  try  hydrochloric  acid  and  zinc,  sulphuric  acid  and 
iron;  mix  equal  parts  of  potassium  chlorate  and  sugar  to- 
gether, place  on  iron  pan,  and  add  a  few  drops  of  sulphuric 
acid,  at  arm's  length.  Add  a  small  piece  of  metallic  sodium 
to  water.  The  hydrogen,  set  free,  ignites  spontaneously. 

32.    FRICTION  AND  COMPRESSION  PRODUCE  HEAT 

When  one  body  rubs  against  another,  there  is  a  certain  re- 
sistance which  depends  upon  the  force  of  contact  and  the 
surface  quality  of  the  bodies.  We  call  the  cause  of  this 
resistance  friction.  Since  the  molecules  which  are  on  the  sur- 
faces of  the  two  bodies  are  caused  to  move  more  rapidly,  heat 
is  produced.  Examples  :  production  of  fire  by  the  rubbing 
together  of  two  sticks,  and  also  by  the  use  of  flint  and  steel. 

If  we  hammer  a  piece  of  lead,  we  force  the  molecules  to  slip 
by  one  another  and  give  them  an  added  velocity,  which 
becomes  apparent  as  heat.  Thus  there  can  be  external  and 
internal  friction,  but  the  result  is  always  a  production  of  heat. 

Since  molecular  motion  is  heat,  we  should  expect  that  if  we 
could  increase  the  number  of  molecules  within  a  given  space, 
the  temperature  would  rise.  The  only  way  in  which  this 
object  can  be  accomplished  is  by  compression.  If  we  com- 
press a  gas,  it  becomes  hotter.  Conversely,  if  the  gas  is  Allowed 
to  expand,  it  becomes  cooler.  Refrigerating  plants  and  ice 
machines  are  founded  on  this  principle.  Ammonia  gas  is 
compressed  and  then  is  allowed  to  expand  in  the  desired 
place,  which  lowers  the  temperature  of  that  place  consider- 


48  INTRODUCTION  TO  GENERAL  SCIENCE 

ably  below  the  freezing  point  of  water.  Carbon  dioxide  may 
be  obtained  in  liquid  form  in  steel  tanks.  If  this  liquid  is 
allowed  to  expand,  so  much  heat  is  required  that  it  turns  to  a 
white  solid  at  a  temperature  of  —80°  C.  Mercury  may  be 
frozen  by  the  removal  of  the  heat  required  to  evaporate 
solid  carbon  dioxide. 

References :  — 

1.  1002 :  393-395.          Heat  of  Sun  Due  to  its  Contraction. 

2.  1103:49-50.  Heating  by  Compression  and  Cooling  by 

Expansion  in  the  Atmosphere. 

3.  1803  :  176.  Heat  Developed  by  Friction. 

4.  1803 :  177-178.          Heat  Produced  by  the  Compression  of  a 

Gas. 

5.  1803  :  178-179.  Cooling  by  Expansion. 

6.  1803 :  210.  Intense   Cold   by  Evaporation   and   Ex- 

pansion. 

a.  1805 :  307-309.  Heat  Produced  by  Friction  and  by  Com- 
pression. 

6.    1807  :  161-162.     Heat  from  Friction. 

c.  1808 : 214-215.  Friction  and  Compression  as  Sources  of 
Heat. 

EXPERIMENTS  FOR  THE  HOME 

Rub  a  coin  on  the  coat  sleeve;  hammer  a  piece  of  lead. 
Notice  that  a  bicycle  pump  becomes  warm,  during  use,  and 
note  that  the  connecting  tube  also  is  heated. 

Try  to  obtain  a  lead  bullet  immediately  after  it  has  struck 
an  iron  target,  and  note  its  appearance  as  well  as  its  tempera- 
ture. Explain  its  appearance.  Why  would  the  results  not 
be  the  same  with  a  wooden  target  ? 

Observe  that  in  all  of  the  given  examples  motion  has  been 
changed  into  heat,  that  is,  molar  or  mass  motion  is  trans- 
formed into  molecular  motion. 


RADIUM  PRODUCES  HEAT  49 

EXPERIMENTS  FOR  THE  TEACHER 

Obtain  a  five-pound  tank  of  carbon  dioxide  and  a  small 
flannel  bag.  Tie  the  bag  over  the  outlet  of  the  tank,  tipping 
the  tank  so  that  the  outlet  is  lower  than  the  rest  of  the  tank. 
Open  wide  the  stopcock  for  half  a  minute.  If  there  is  not 
enough  solid,  repeat.  Put  some  mercury  in  a  test  tube  and 
place  the  test  tube  in  a  beaker  half  full  of  ether,  containing 
the  carbon  dioxide.  When  the  mercury  is  frozen,  break  the 
test  tube  and  drop  the  solid  mercury  on  the  table  like  any 
common  metal. 

33.    RADIUM  PRODUCES  HEAT 

Radium  was  for  some  time  one  of  the  curiosities  of  the 
chemical  world.  Since  it  produced  elements  different  from 
itself,  it  seemed  to  be  an  exception  to  general  rules  governing 
elements.  We  now  know  that  other  elements  act  in  a  similar 
manner,  although  not  to  such  a  marked  degree. 

Radium  can  produce  chemical  changes  in  a  covered  photo- 
graphic plate,  and  excite  fluorescence  in  some  substances. 
This  is  accomplished  by  the  emission  of  rapidly  moving  par- 
ticles and  by  some  rays  which  are  similar  to  Rontgen,  or 
X-rays.  The  particles  form  a  gas  called  helium. 

Since  heat  is  due  to  the  motion  of  the  molecules,  the  libera- 
tion of  rapidly  moving  particles  produces  so  much  heat  that 
the  temperature  of  radium  is  always  5°  F.  or  2.7°  C.  higher 
than  its  surroundings.  The  amount  of  heat  liberated  by  one 
gram  of  radium  is  100  calories  per  hour.  Thus  radium  can 
melt  one  and  one  fourth  of  its  own  weight  of  ice  every 
hour.  It  is  not  possible  to  utilize  this  heat  for  practical 
purposes. 


50 


INTRODUCTION  TO  GENERAL  SCIENCE 


References :  — 

1.  1002:396. 

2.  1803:476-482. 

a.  1001:157. 

b.  1809:434. 


Theory  —  Heat  of  Sun  Partly  Due  to  Radium, 
Radium  and  its  Transformations. 
Contraction  and  Radium  Produce  Sun's  Heat. 
Heat  from  Radium. 


34.    THE  SUN 

Our  sun  is  a  vast  sphere,  one  hundred  and  ten  times  the 
diameter  of  the  earth,  and  more  than  one  million  times  its 
volume.  It  rotates  on  its  axis  once  in  twenty-five  and  one 
fourth  days,  and  is  distant  about  ninety-two  million  miles. 
It  is  so  hot  that  all  the  material  of  which  it  is  composed  exists 
in  the  form  of  a  gas  or  vapor.  The  heat  is  probably  caused 
by  a  contraction  due  to  gravitation,  the  compression  being 
sufficient  to  produce  the  high  temperature.  The  emanations 
from  radium  may  produce  some  of  the  heat,  as  radium  has 
been  discovered  in  the  sun. 


References :  — 

1.  1002:105-106. 

2.  1002:387-390. 

3.  1002:390-391. 

4.  1002:410-116. 

5.  1103:25. 

6.  1304:9-10. 

7.  1601:3-9. 

a.  1001:154-155. 

6.  1001 :  155-156. 

c.  1001:156-157. 

d.  1001 :  157-160. 

e.  1003:110-111. 
/.  1004:166-167. 
g.  1004:  168-169. 


Heat  of  Sun. 

Heat  of  Sun. 

Temperature  of  Sun. 

Constitution  of  Sun. 

The  Apparent  Motion  of  the  Sun  around 

the  Earth. 

Heat  of  Solar  System. 
Sunshine. 

Temperature  of  the  Sun. 
Constancy  of  Sun. 
Age  of  Sun. 
Constitution  of  Sun. 
Source  and  Duration  of  Sun's  Heat. 
Temperature  of  Sun. 
Age  of  Sun  and  Maintenance  of  Heat. 


THE  SUN  THE  SOURCE  OF   ALL   ENERGY          51 

h.  1207 :  253-257.  The  Sun  as  a  Source  of  Heat. 

i.  1301 :  55-57.  Heat  of  Sun. 

j.  1807  :  211.  Source  of  the  Sun's  Energy. 

k.  1810 :  398.  Composition  of  the  Sun. 

35.    THE  SUN  THE  SOURCE  OF  ALL  ENERGY 

As  previously  stated,  the  sun  sends  out  energy,  which  is 
transformed  into  various  other  kinds  of  energy.  It  is  quite 
probable  that  the  original  energy  is  electrical,  and  that  its 
products  depend  upon  the  various  conditions  it  meets.  These 
products  may  be  enumerated  as  follows :  — 

1.  The  Sensation  of  Light.     Light  in  itself  is  invisible.     Cer- 
tain wave  lengths  of  electrical  energy  enter  the  eye  and  pro- 
duce their  effect,  according  to  the  length  of  the  waves,  and  the 
amount  of  energy  which  affects  the  retina,  or  sensitive  part 
of  the  eye.     We  see  objects  by  reflected  light.     We  really  do 
not  see  the  objects  themselves.     All  light  produced  on  earth 
owes  its  energy  originally  to  the  sun. 

2.  Heat.     This  is  produced   when  the    electrical    energy 
strikes  anything  which  retards  it.      If  it  strikes  an  opaque 
object,  all  the  energy  is  stopped,  and  the  result  is  the  great- 
est possible  amount  of  heat.     If  the  object  is  transparent, 
most   of   the  energy   will  pass  through;  very  little  will  be 
stopped,  and  the  material  will  not  become  very  warm.     The 
amount  of  heat  produced  by  the  energy  of  the  sun  varies  from 
a  very  little,  in  the  case  of  transparent  material,  to  a  great 
deal,  in  the  case  of  opacity.     An  excellent  example  of  this  is 
to  notice  how  warm  we  become  when  we  stand  by  a  closed 
window  in  the  sunshine,  and  then  to  observe  that  the  glass, 
through  which  this  energy  comes,  is  quite  cold.     This  is  ab- 
solute proof  that  heat  from  the  sun  does  not  come  to  us  as 
heat,  but  as  energy,  which  is  doubtless  electrical. 


52  INTRODUCTION  TO  GENERAL  SCIENCE 

3.  Change  in  chemicals,  which  enable  us  to  use  the  art  of 
photography,  and  other  changes,  a  study  of  which  belongs 
particularly  to  a  chemistry  course. 

4.  In  plants  also,  much  of  the  growth,  and  nearly  all  of  the 
nourishment,  are  dependent  upon  chemical  changes  which  the 
energy  of  the  sun  causes  in  them.      Plants  cannot  take  up  the 
carbon  from  the  air,  nor  can  they  change  starch  to  sugar, 
necessary  for  plant  growth,  without  the  sunlight  or  some 
other  very  powerful  light,  as,  for  instance,  the  electric  arc. 

5.  Electrical  energy  from  the  sun  probably  causes  terres- 
trial magnetism.     It  has  been  noticed  whenever  there  are  sun 
spots  that  the  magnetism  is  affected,  proportionally  to  the 
size  and  duration  of  the  sun  spots.     In  this  connection  it  is 
quite  likely  that  the  aurora  borealis  and  the  aurora  australis 
owe  their  existence  to  the  same  cause. 

References :  — 

1.  1002 :  414-416.          Description  of  Sun  Spots. 

2.  1103  :  27.  Solar  Constant. 

a.  1001 :  124-127.  Nature  of  Sun  Spots. 

6.  1001 :  131-132.  Cause  and  Influence  of  Sun  Spots. 

c.  1003:106-110.  Sun  Spots  Show  Rotation  of  Sun. 

d.  1004 :  143-144.  Terrestrial  Influence  of  Sun  Spots. 

e.  1207  :  74^75.  Explanation  and  Effects  of  Sun  Spots. 
/.  1301 :  53-54.  Magnetism  and  the  Northern  Lights. 
g.  1306  :  8.  Sun  Spots. 

h.   1806 :  376-378.     The  Sun  our  Main  Source  of  Energy. 

36.    THEORIES 

From  time  immemorial,  man  has  wondered  about  the  laws 
and  phenomena  of  nature.  His  conjectures,  somewhat  hazy 
at  first,  and  more  scientific  as  the  ages  passed,  always  con- 
cerned the  same  questions :  the  source  of  the  world;  why  the 


THE  LAWS  OF   MOTION  53 

world  revolved;  whether  the  world  was  always  in  its  present 
state;  what  the  stars  were;  what  the  sun  was.  The  conclu- 
sions that  he  drew  were  at  first  very  erroneous,  as  any  student 
of  mythology  knows.  Yet  the  great  thinkers,  working  from 
what  they  learned  through  history,  physics,  chemistry,  have 
formulated  certain  theories  which  may  explain  our  solar 
system  and  its  formation.  There  is  hardly  a  scientist  who 
will  have  the  temerity  to  say  that  any  given  theory  is  abso- 
lutely correct,  yet  all  these  theories  are  very  reasonable  and 
are  supported  by  such  an  immense  number  of  facts  that  they 
are  probably  correct  to  a  very  great  extent.  Theories  must 
precede  practice,  and  are  very  valuable  as  a  starting  point 
for  scientific  investigation. 

References :  — 

1.    1002 :  441-443.  The  Advantages  of  Theories, 

a.    1701  : 64.  Value  of  a  Theory. 

6.    1705  :  89-90.  The  Necessity  of  Theories. 

c.  1712  :  7.  The  Definition  of  a  Hypothesis. 

d.  1801 :  3.  Theory  Denned. 

e.  1807 : 145.  The  Meaning  and  Value  of  a  Theory. 
/.    1808:11.  Hypotheses,  Theories,  Laws. 

g.   1809 :  5-6.        The  Theoretical  Methods  of  Physics. 

37.   THE  LAWS  OF  MOTION 

All  heavenly  bodies  obey  the  laws  of  nature  in  the 
same  way  as  do  small  bodies.  It  may  be  well  to  consider 
what  is  meant  by  the  law  of  nature,  or,  as  it  is  sometimes 
called,  natural  law.  A  man-made  law  is  a  rule  of  conduct; 
nature's  laws,  as  they  are  formulated  by  man,  are  merely 
statements  of  facts.  Man  has  made  the  discovery  that  cer- 
tain results  come  from  certain  causes.  His  discovery  does 
nor  make  nature  act  that  way,  for  nature  has  always  acted 


54  INTRODUCTION  TO  GENERAL  SCIENCE 

in  the  same  way.  Thus,  when  we  study  any  natural  law,  we 
must  not  for  a  moment  think  that  nature  has  to  act  that  way, 
but  simply  that  nature  does  act  that  way,  and  that  in  these 
laws  there  never  have  been,  and  never  will  be,  any  exceptions. 
The  laws  of  motion  are  absolutely  unalterable,  and  were 
discovered  and  stated  first  by  Sir  Isaac  Newton.  They  are, 
therefore,  called  "  Newton's  Laws  of  Motion,"  but  Newton 
did  not  make  them.  His  experiments  showed  him  that 
bodies  in  motion  always  behaved  in  a  certain  way,  and  he  put 
his  observations  into  concise  form  and  called  them  the  "  Laws 
of  Motion." 

References :  — 

1.  1002  : 145-147.      The  Laws  of  Motion. 

2.  1803 :  32-36.          Newton's  Laws  cf  Motion. 

a.  1001 :  72.  The  Law  of  the  Earth's  Motion. 

6.  1003  :  81-82.  The  Laws  of  Motion. 

c.  1801 :  29-31.  The  Laws  of  Motion. 

d.  1802  :  56.  Newton's  Laws  of  Motion. 

e.  1804 :  65-69.  Newton's  Three  Laws  of  Motion. 
/.  1805  :  49-50.  The  Laws  of  Motion. 

g.  1807 :  83-92.  The  Laws  of  Motion. 

h.  1808 :  39.  Newton's  Laws  of  Motion. 

i.  1809 :  65-72.  Laws  of  Motion. 

j.  1810 :  36-37.  Newton's  Laws  of  Motion. 

Experiment  20.  —  Inertia  and  Reaction. 

Apparatus:  Card,  coin,  iron  ball  with  screw  eyes  at  the 
two  ends  of  a  diameter,  string,  a  piece  of  clock  spring,  two 
small  blocks  of  wood  of  unequal  size. 

a.  Balance  coin  on  card  on  end  of  finger,  and  snap  card 
out.     Coin  will  remain  on  finger,  if  care  is  used.     If  this  is 
found  to  be  too  difficult,  place  coin  on  card  on  corner  of  a 
table,  and  knock  the  card  off,  horizontally. 

b.  Support  iron  ball  by  small  string  and  tie  another  piece 


EFFECTS  OF  FORCES  ACTING  AT  THE  SAME  TIME     55 

to  the  under  side  of  the  ball.  Pull  slowly  on  the  bottom  string, 
Which  string  breaks?  Why?  Pull  very  suddenly  on  the 
lower  string,  and  explain  results. 

c.  Bend  a  piece  of  clock  spring  about  eight  inches  long  into 
the  form  of  a  V.  Put  it  between  two  blocks,  of  unequal  size, 
compress  and  release.  Note  the  different  distances  which 
the  blocks  moved.  Repeat  this  several  times,  and  give  an 
explanation. 

38.    EFFECTS  OF  Two  OR  MORE   FORCES  ACTING  AT  THE 

SAME  TIME 

If  two  or  more  forces  are  acting  on  a  body,  each  force  acts 
independently  of  all  the  other  forces.  That  is,  the  final  posi- 
tion of  the  body  will  be  -the  same  as  it  would  have  been  if  one 
force  had  acted  alone,  stopped,  and  then  each  of  the  other 
forces  had  acted  successively. 

This  fact  is  stated  in  Newton's  Second  Law  of  Motion. 
Examples  are  everywhere  present  if  we  do  but  notice  them. 
For  instance,  when  a  person  crosses  a  moving  car,  the  final 
position  he  will  occupy  will  be  the  same  as  it  would  have  been 
if  he  had  crossed  the  car  after  it  stopped.  The  graphical 
representation  of  two  or  more  forces  acting  together  is  given 
in  Section  97,  Resolution  of  Forces. 

References :  — 
Any  reference  in  Section  37. 

EXPERIMENT  FOR  THE  TEACHER 
Newton's  Second  Law  of  Motion 

Use  the  standard  machine  to  illustrate,  and  repeat  at  least 
three  times,  trying  the  different  positions  of  the  trigger.  Be 
sure  that  the  machine  is  horizontal. 


56  INTRODUCTION  TO  GENERAL  SCIENCE 


39.    UNIVERSAL  GRAVITATION 

Gravitation  is  the  name  given  to  the  force  which  acts  among 
all  bodies  of  matter,  tending  to  bring  them  together.  We 
who  live  on  the  earth  are  inclined  to  think  that  the  earth 
attracts  us.  While  this  is  true,  it  is  just  as  much  a  fact  that 
the  earth  is  attracted  by  us.  Gravitation,  then,  is  the  mutual 
action  which  takes  place  between  every  two  bodies  of  matter. 
By  careful  measurements,  it  has  been  found  that  the  changes  of 
gravitation  vary  as  the  product  of  the  masses  of  the  two  bodies, 
and  inversely  as  the  square  of  the  distance  between  them. 

Not  only  is  this  force  of  gravitation  acting  between  the  earth 
and  the  bodies  on  it,  but  it  acts  between  all  of  the  heavenly 
bodies.  Thus  the  sun  attracts  the  earth,  and  the  earth  at- 
tracts the  sun ;  the  moon  attracts  the  earth,  and  the  earth 
attracts  the  moon.  The  question  which  naturally  arises  is, 
Why  do  not  these  bodies  come  together?  The  answer  is 
that  they  would  come  together  if  they  were  not  in  rapid 
motion,  whirling  around  each  other.  Part  of  the  year  the 
earth  and  the  sun  do  come  closer  together  than  at  other 
seasons,  but  the  velocity  of  the  earth  is  great  enough  to  take 
it  entirely  around  the  sun,  and  thus  avoid  any  collision. 
This  is  one  of  the  proofs  that  the  earth  revolves  around  the 
sun  once  a  year,  for  if  this  revolution  did  not  take  place,  the 
earth  and  the  sun  would  fall  together.  Yet  as  the  earth  re- 
volves around  the  sun,  its  path  is  riot  that  of  a  smooth  curve, 
nor  is  it  the  same  from  year  to  year.  The  other  planets  at- 
tract the  earth,  and  the  earth  attracts  the  other  planets,  so 
that  the  earth  moves  in  a  wavy  path  approximating  an  ellipse. 
In  the  same  way,  the  moon  does  not  revolve  around  the  earth 
in  a  symmetrical  curve,  but  moves  in  a  wavy  path. 


THE  CENTER  OF  GRAVITY  57 

References :  — 

1.  1002  :  194-200.  The  Law  of  Gravitation. 

2.  1304 :  8-9.  Gravity  and  Gravitation. 

3.  1803 :  20-21.  Newton's  Law  of  Universal  Gravitation. 
a.   1001:51.  Gravity. 

6.    1801 :  48.  Law  of  Universal  Gravitation. 

c.  1802 :  86.  Law  of  Universal  Gravitation. 

d.  1804 : 118-121.     Universal  Attraction  between  Masses. 

e.  1805 :  48-49.  Gravitation. 

/.   1806 :  91-92.  Direction  of  Gravitation  and  Center  of 

Gravity. 

g.    1807 :  98-99.  Universal  Gravitation. 

h.    1808 :  60-61.  Gravitation  and  Gravity. 

i.    1809 :  110.  Newton's  Law  of  Universal  Gravitation. 
j.    1810 :  33-34.          Universality  of  Gravitation. 

k.  1811:330-335.  Gravitation. 


40.    THE  CENTER  OF  GRAVITY 

The  center  of  gravity  is  the  point  which,  if  supported,  will 
prevent  the  entire  body  from  falling.  It  may  also  be  defined 
as  that  point  where  we  may  consider  all  the  weight  of  the 
body  located.  In  a  sphere  it  is  at  the  center;  with  an  irregu- 
lar body  the  center  of  gravity  may  be  entirely  outside  the 
body. 

The  center  of  gravity  of  a  small  body  may  be  located  by 
suspending  the  latter  by  a  string.  If  the  string  is  imagined 
to  be  prolonged  into  the  body,  it  will  pass  through  the  center 
of  gravity.  By  supporting  the  body  from  at  least  three  dif- 
ferent points,  the  center  of  gravity  is  definitely  determined. 

References :  — 

1 .    1803  :  22-23.  Center  of  Gravity  and  Method  of  Finding  It. 

a.    1801 :  48-49.  Center  of  Gravity. 

6.   1805 :  50.  Center  of  Gravity. 


58  INTRODUCTION  TO  GENERAL  SCIENCE 

c.  1806 :  92-93.     Center  of  Gravity. 

d.  1807  :  60-61.     Center  of  Gravity. 

e.  1808  :  63-64.     Center  of  Gravity. 

/.     1809 :  85-86.    Center  of  Gravity  and  Methods  of  Locat- 
ing It. 
g.    1810 :  13-14.     Center  of  Gravity  and  Method  of  Finding  It. 

Experiment  21.  —  Center  of  Gravity. 

Apparatus :  Bottle,  two  cork  stoppers,  two  knives  or  table 
forks,  pin,  needle. 

a.  Place  one  stopper  in  the  bottle  and  stick  the  pin  into  it. 
Into  one  end  of  the  other  cork  push  the  needle,  head  first,  and 
stick  the  knives  or  forks  into  the  opposite  sides  of  the  cork  so  that 
they  hang  in  a  slanting  direction.  If  the  point  of  the  needle 
is  placed  on  the  head  of  the  pin,  the  whole  system  will  balance. 
Devise  some  method  of  balancing  a  half  dollar,  on  its  edge,  on 
the  rim  of  a  table  glass.  If  the  center  of  gravity  of  any  sys- 
tem is  low,  the  whole  system  is  stable  and  will  balance. 

41.  THE  EFFECT  OF  Two  FOKCES  ACTING  AT  RIGHT 
ANGLES  TO  EACH  OTHER 

The  second  law  of  motion  states  that  each  force  acts  inde- 
pendent of  any  other  force.  See  Section  38.  If  the  forces 
act  at  right  angles  to  each  other,  a  curved  motion  is  produced 
which  may  be  a  closed  curve,  like  the  circle  or  the  ellipse,  or 
an  open  curve,  of  which  the  parabola  and  the  hyperbola  are 
examples. 

The  earth  is  held  in  its  path  around  the  sun  by  means  of 
the  attraction  which  the  earth  and  sun  have  for  each  other, — 
gravitation,  —  while  its  forward  motion  continues  on  account 
of  its  inertia.  Refer  to  Section  37.  A  more  complete  dis- 
cussion of  the  earth's  motions  is  given  in  Section  50,  The 
Motions  of  the  Earth. 


THE  MEASUREMENT  OF   ROTARY   MOTION        59 

If  the  forward  motion  of  a  body,  either  on  earth  or  in  the 
heavens,  is  great  compared  with  the  force  of  attraction,  the 
body  passes  beyond  the  effective  action  of  the  latter  force, 
and,  in  the  case  of  the  heavenly  bodies,  may  never  return. 
Some  comets  act  in  this  manner.  See  Section  57,  Comets. 

References :  — 

1.    1803  :  19-20.  Pendulum  Motion  Analyzed. 

a.  1801 :  60.  Curvilinear  Motion. 

b.  1804 :  24-25.  Rectilinear  and  Curvilinear  Motion. 

c.  1805  :  63.  Motion  of  a  Pendulum. 

d.  1807  :  93-97.  Curvilinear  Motion. 

e.  1808  :  49.  Curvilinear  Motion. 
/.    1809  :  113.  Curvilinear  Motion. 

EXPERIMENT  FOR  THE  HOME 

Swing  a  stone  at  the  end  of  a  weak  string.  Note  the  pull 
which  is  necessary  to  make  the  stone  continue  in  a  circular 
path. 

Make  the  stone  revolve  faster  until  the  string  breaks.  In 
this  case  the  forward  motion  is  too  great  for  the  force  acting 
at  right  angles  to  it  to  be  affected  by  the  pull  of  the  string. 
Note  that  the  stone  moves  off  in  a  straight  path.  This  is  due 
to  the  fact  that  the  effect  of  the  string  ceases  as  soon  as  the 
string  breaks.  Gravitation  decreases  gradually,  and,  even  in 
the  case  of  very  rapidly  moving  comets,  produces  a  slightly 
curved  path. 

42.    THE  MEASUREMENT  OF  ROTARY  MOTION 

The  motion  produced  by  turning  a  body  on  an  axis  is  called 
rotary  motion.  If  a  certain  point  on  the  outside  of  the  body 
moves  until  it  returns  to  its  original  position,  we  say  that  the 


60  INTRODUCTION  TO  GENERAL  SCIENCE 

body  has  made  one  revolution.  It  is  easy  to  count  the  revo- 
lutions, but  we  sometimes  desire  to  measure  rotary  motion  in 
fractions  of  a  revolution. 

A  complete  revolution  is  called  360°.  One  quarter  of  a 
revolution,  therefore,  is  90°.  Each  degree  is  divided  into 
60  equal  parts  called  minutes,  meaning  small.  The  minute 
was  found  not  to  be  small  enough,  and  a  second  division  was 
made  which  consists  of  the  60  equal  parts  of  the  minute, 
which  are  called  seconds. 

Not  only  is  rotary  motion  measured  by  this  means,  but  the 
same  system  is  used  to  indicate  direction.  Thus  a  road  may 
cross  another  road  at  what  is  called  an  angle  of  30°.  This 
means  that  a  wagon,  in  going  from  one  road  to  the  other, 
must  turn  30°  in  order  to  take  the  desired  direction.  We 
reckon  direction,  in  regard,  to  the  north  and  south  line,  by 
this  same  system.  See  Sections  49  and  61. 

Altitude  may  be  given  in  feet,  or  other  units  of  length,  or  it 
may  be  stated  in  degrees,  minutes,  and  seconds.  We  can  say 
that  a  building  is  62°  high,  from  a  certain  position,  which 
means  that  it  is  necessary  to  raise  our  eyes  62°  above  the 
horizontal  plane  in  order  to  see  the  top  of  the  building. 

References :  — 

Any  text  in  Geometry.    See  Angular  Measurement. 
1.  Forest  Service  Bulletin  36  :  98-106.    Instruments  for  Measur- 
ing Heights. 

Experiment  22.  —  To  Make  and  Use  a  Clinometer. 

a.  On  a  piece  of  cigar-box  wood  6"  X  4"  draw  a  semicircle 
with  the  center  at  the  middle  of  the  long  side.  Mark  every 
5°  with  the  protractor  and  number  from  the  right  angle  mark, 
each  way,  0-90. 

Drive  a  brad  at  the  center  of  the  semicircle  and  one  at  each 


THEORIES  OF  EVOLUTION  OF  SOLAR  SYSTEM    61 

90°  mark.  Tie  a  small  weight  to  the  middle  brad,  using  a  piece 
of  string  more  than  6"  long.  When  the  three  brads  are 
horizontal,  the  string  should  cross  the  0  degree  mark. 

b.  Holding  the  instrument  in  the  left  hand,  sight  along  the 
three  brads  at  some  elevated  object  and  read  where  the  string 
crosses  the  degree  marks.     This  is  the  angular  altitude  from 
that  position.     Approach  the  object  and  again  sight.     Why 
is  there  a  difference  ?     Has  the  object  become  taller  ? 

c.  "  Sight  "  at  the  sun.     To  do  this  hold  a  piece  of  paper 
near  one  end  of  the  clinometer  and  obtain  the  three  shadows 
of  the  brads  in  the  same  place.     The  reading  indicates  the 
altitude  of  the  sun.     Walk  toward  the  sun  and  obtain  its  al- 
titude.    Is  there  any  difference?     Explain.     Wait  half  an 
hour  and  repeat,  giving  an  explanation  of  the  results. 

43.    THEORIES  OP  THE  EVOLUTION  OF  THE  SOLAR  SYSTEM 

There  are  two  general  theories  which  must  not  be  accepted 
as  facts,  but  as  theories.  There  is  much  which  supports  each 
of  these  theories,  and  likewise  there  are  many  things  which 
are  not  explained  by  either  of  them. 

La  Place  formulated  a  Ring  Hypothesis,  which,  stated 
briefly,  is  as  follows:  In  the  beginning  there  was  a  large 
mass  of  heated  gaseous  material  which  began  slowly  to  revolve, 
and  as  it  cooled  it  contracted.  As  the  contraction  took  place 
the  motion  became  faster  and  faster,  until  the  centrifugal 
force  was  greater  than  the  gravitational  force,  so  that  a  ring 
around  its  equator  was  thrown  off  into  space.  Ring  after 
ring  left  the  parent  mass,  each  ring  contracting  into  a  sphere, 
one  of  which  is  the  earth.  The  other  planets  were  formed  in 
the  same  way.  There  remained  a  central  mass,  which  is  our 
present  sun. 


62  INTRODUCTION  TO  GENERAL  SCIENCE 

Lockyer  and  Darwin  modified  this  theory  by  considering 
that  the  material  originally  was  in  the  form  of  cold  meteors. 
These,  on  account  of  the  distance  between  the  separate 
meteors,  would  act  like  a  gas,  and  the  heat  could  have  been 
produced  by  the  collision  and  compression  of  a  large  number 
of  these  meteors.  Thus  there  was  no  necessity  for  original 
heat.  This  theory  has  been  given  the  name  Meteoritic  Hy- 
pothesis. 

Lastly,  a  modification  of  the  La  Place  Hypothesis  states 
that  the  material  was  not  in  equilibrium  at  the  beginning,  but 
whirling  in  a  vast  spiral,  the  different  parts  of  the  spiral  break- 
ing up  to  form  the  Solar  System.  This  is  called  the  Spiral 
Nebular  Hypothesis. 

Since  we  are  considering  the  beginning  of  things,  a  defini- 
tion of  the  word  evolution  might  not  be  out  of  place.  By 
evolution  is  meant  the  slow  change  from  the  simple  and  un- 
organized to  the  complex  and  highly  organized.  Such  a 
change  usually  takes  a  very  long  period  of  time,  which  cannot 
be  reckoned  in  years,  but  in  millions  of  years. 

References :  — 

1.  1002 :  446-449.  La  Place  Ring  Hypothesis. 

2.  1002  :  448.  Meteoritic  Hypothesis. 

3.  1002  :  453-458.  La  Place  Ring  Hypothesis. 

4.  1002  :  463-466.  Spiral  Nebular  Hypothesis. 

5.  1002  :  485-487.  The  Past  and  Future  of  the  Solar  System 

6.  1205  :  304-305.  The  Earth's  Beginnings. 

a.  1001 :  353-356.  Genesis  and  Nebular  Hypothesis. 

6.  1003  :  224.  The  Nebular  Hypothesis. 

c.  1004 :  351-353.  La  Place's  Nebular  Hypothesis. 

d.  1004 :  353-354.  Lockyer's  Meteoritic  Hypothesis. 

e.  1301 :  27-31.  The  Nebular  Hypothesis. 
/.  1305 :  38.  The  Nebular  Theory. 

g.    1306 :  19-22.         The  Nebular  Hypothesis. 


THE  PLANETS  AND   THE  EARTH  63 

44.    THE  SOLAR  SYSTEM 

Up  to  this  time  we  have  looked  at  natural  phenomena  from 
a  personal  standpoint.  We  will  now  consider  the  real  place 
which  we,  on  earth,  occupy  in  the  great  system  of  which  we 
are  such  a  small  part. 

The  solar  system  consists  of  the  sun  and  the  following 
planets,  named  in  the  order  of  their  distances  from  the  sun: 
Mercury,  Venus,  Earth,  Mars,  Jupiter,  Saturn,  Uranus, 
Neptune.  It  is  called  solar,  because  all  of  these  planets  re- 
volve around  the  sun,  and  a  system,  because  they  obey  definite 
laws,  returning  upon  their  orbits  at  regular  intervals. 

References :  — 

1.  1002 :  485-487.          The  Age  and  Future  of  the  Solar  System. 

2.  1304 :  3-6.  Other  Spheres. 

a.  1001 :  359-360.  Age  and  Duration  of  Solar  System. 

6.  1003 :  142-144.  The  Structure  of  the  Solar  System. 

c.  1004  :  188-189.  The  Planetary  System. 

d.  1004  :  191-192.  Gravitation  Explains  Planetary  Motion. 

e.  1301:22-27.  The  Solar  System. 
/.  1303  :  14.  The  Solar  System. 
g.  1305  :  35-38.  The  Solar  System. 

h.   1306 : 5-13.  The    Solar  System,  the   Earth,  and   the 

Moon. 

i.    1307 :  9-14.  The  Earth  among  Planets]  and  the  Sun. 

j.    1309  :  11-17.  The  Earth  and  the  Solar  System. 

k.  1310 :  320-321.  The  Solar  System  and  the  Stars. 

I.    1311:17-18.  The  Earth  is  One  of  the  Planets. 

m.  1312 :  2.  What  the  Solar  System  Comprises. 

45.    THE  PLANETS  AND  THE  EARTH 

These  large  bodies  of  matter  are  cold,  and  shine  only  by 
reflected  light,  similar  to  the  light  received  from  the  moon. 
The  planets  may  support  life  according  to  the  conditions  of 


64 


INTRODUCTION  TO  GENERAL  SCIENCE 


the  atmosphere  and  the  supply  of  water.  They  all  rotate  on 
axes,  and  revolve  around  the  sun.  Thus  they  have  day  and 
night,  and  seasons,  although  all  these  periods  are  entirely 
different  from  those  of  the  earth,  in  length,  in  degree,  and 
frequency  of  changes. 

Since  we  live  on  the  earth,  we  do  not  think  of  it  as  a  sphere 
revolving  through  space,  for  it  is  so  large  that  the  small  part 
we  see  at  one  time  seems  flat,  while  the  sun  and  the  stars  ap- 
pear to  move  around  the  earth.  Nevertheless,  the  earth 
behaves  like  the  other  planets,  and  is,  after  all,  one  of  the 
smallest  ones,  Mars  and  Mercury,  only,  being  smaller. 

References :  — 

Size  of    the  Sun  and  Distances  of  the 

Planets. 

The  Earth  as  a  Planet. 
The  Planets  in  General. 
Revolution  of  the  Earth  around  the  Sun. 
Structure  of  the  Solar  System. 
The  Planets. 
The  Earth  as  a  Globe. 
Relation  of  Earth  to  Other  Planets. 
The  Earth  as  a  Planet.  • 
Rotation  of  the  Earth. 
Revolution  of  the  Earth. 
The  Relation  of  the  Earth  to  the  Planets 

and  the  Sun. 
k.  1307 : 10-14.         The  Earth  among  Planets. 


1.  1002:293-297. 

2.  1304:1-8. 

a.  1001 

:  199-201. 

b.  1003 

:  32-37. 

c.  1003 

:  142-145. 

d.  1301 

:  23-27. 

e.  1303 

:l-8. 

/.  1303 

:  12-14. 

g.  1305 

:  38-41. 

h.  1305 

:  43-44. 

i.  1305 

:  48-49. 

j.  1306 

:  3-18. 

46.    AGE  OF  THE  EARTH 

The  age  of  the  earth  must  be  very  great,  so  great  as  to  be 
reckoned  in  millions  of  years.  We  know  that  this  is  so,  for  the 
changes  which  have  taken  place  upon  the  surface  of  the  earth 
could  not  have  been  accomplished  in  any  short  period  of  time. 


THE  SHAPE  AND  SIZE  OF  THE  EARTH     65 

We  know  that  the  material  of  which  the  mountains  are  com- 
posed was  first  worn  away  by  streams  and  then  collected  at 
the  bottom  of  the  ocean,  where  it  remained  for  thousands  of 
years.  Later,  by  vast  and  probably  slow  convulsions  of  the 
earth's  surface,  it  was  raised  to  an  elevation  far  above  the 
present  height  of  mountains.  During  additional  thousands 
of  years  these  elevations  were  worn  down  to  their  present 
condition.  We  have  only  to  observe  the  erosion  of  rocks  by 
a  stream  to  realize  that  the  changes  such  action  involves  are 
hardly  appreciable  in  a  lifetime.  All  the  manifest  alterations 
of  the  surface  of  the  earth  could,  therefore,  have  been  accom- 
plished only  in  an  incredible  length  of  time.  Moreover,  they 
must  have  taken  place  after  the  earth  finally  became  cool 
enough  for  water  to  remain  on  it. 

References :  — 

1.  1205  :  291-294.          The  Age  of  the  Earth  as  Shown  by  For- 

mations. 

2.  1205  :  296-297.          Fossils  and  what  they  Teach. 

3.  1205:298-303.  Age    Great,  Known  by  Slow  Change  of 

Species. 

4.  1304T45-46.  Age  of  the  Earth. 

a.  1201 :  13-17.  The  Beginning  of  the  Earth. 

6.  1203  :  150-160.  Fossils  and  their  Teachings. 

c.  1206  :  455-457.  Age  Determined  from  Nebular  Hypothesis. 

d.  1210  :  260.  The  Seven  Ages  of  the  Earth. 

e.  1301 :  236-239.  Age  of  the  Earth  in  Geological  Series. 
/.  1303 : 11.  Age  of  the  Earth. 


47.    THE  SHAPE  AND  SIZE  OF  THE  EARTH 

For  many  centuries  the  earth  was  considered  flat,  and  it 
was  believed  that  the  sun  went  around  it.     We  now  know 
that  the  sun  does  not  pass  around  the  earth,  that  the  earth 
p 


66  INTRODUCTION  TO  GENERAL  SCIENCE 

is  spherical,  and  that  its  rotation  on  its  axis  is  what  gives  the 
apparent  motion  to  the  sun.  We  have  some  very  certain 
proofs  that  the  earth  is  spherical:  we  know  that  the  earth 
can  be  circumnavigated,  and,  moreover,  the  shadow  of  the 
earth  upon  the  moon,  no  matter  when  it  occurs,  always  has  a 
circular  shape.  Again,  if  the  earth  were  flat,  the  time  of  sun- 
rise and  sunset  would  be  the  same  everywhere;  but  we  know 
that  such  is  not  the  case.  The  higher  we  climb  upon  a  hill, 
or  rise  in  a  balloon,  the  farther  we  can  see.  This  is  true  only 
because  the  earth  is  spherical.  The  amount  of  curvature  of 
the  earth  in  feet  may  be  found  for  the  first  few  miles  by 
squaring  the  number  of  miles  and  multiplying  by  two  thirds. 
The  shape  of  the  eartn  is  not  an  exact  sphere,  but  is  called  an 
oblate  spheroid,  having  a  polar  axis  twenty-seven  miles  less 
than  the  equatorial  diameter.  Thus  the  land  at  the  poles  is 
thirteen  and  one  half  miles  nearer  the  center  of  the  earth  than 
any  point  on  the  equator. 

References :  — 

1.  1002:114-119.  Shape  of  the  Earth. 

2.  1002 : 126-127.  Size  of  the  Earth. 

3.  1304 :  1-3.  Shape  and  Size  of  the  Earth, 
a.    1001 :  46-47.  Size  of  the  Earth. 

6.  1001 :  52-53.  Methods  of  Determining  the  Earth's  Form. 

c.  1001 :  56.  Shape  and  Rotation  of  the  Earth. 

d.  1001 :  58.  Surface  and  Volume  of  the  Earth. 

e.  1303  :  1-5.  Shape  and  Size  of  the  Earth. 
/.  1305  :  38-41.  Shape  and  Size  of  the  Earth. 
g.  1306  :  3-5.  Form  and  Size  of  the  Earth. 
h.  1307 : 14-15.  Form  and  Size  of  the  Earth. 

i.    1309 :  18-22.     Shape,  Size,  and  Density  of  the  Earth. 

j.    1311 :  1-2.         Form  of  the  Earth. 

k.  1312 : 16-18.     Shape  and  Size  of  the  Earth. 


THE  HEAT  OF   THE  EARTH  67 

48.    THE  HEAT  OF  THE  EARTH 

We  realize  that  the  earth  is  very  hot  inside  when  we  think 
of  volcanoes  or  even  hot  springs.  In  most  mines  the  tempera- 
ture increases  one  degree  every  fifty  or  sixty  feet.  If  this 
were  continued,  the  temperature  at  the  center  of  the  earth 
would  be  enormously  high,  but  it  is  probable  that  at  a  depth 
of  one  hundred  and  fifty  miles  the  maximum  is  reached.  This 
is  estimated  to  be  seven  thousand  degrees  F.  The  heat  of  the 
earth  is  probably  maintained,  to  a  certain  extent,  by  radium. 

Since  we  know  that  anything  which  is  hot  gradually  loses 
its  heat,  we  can  reckon  backwards  and  conclude  that  the 
earth  once  must  have  been  extremely  hot.  We  cannot  be 
sure,  however,  just  how  hot  the  earth  has  been.  Neverthe- 
less, we  can  believe  that  it  was  once  in  a  molten  condition. 
References :  — 

1.  1002  :  133-135.        The  Condition  of  the  Interior  of  the  Earth. 

2.  1205  :  277-280.        Conditions  of  the  Interior  of  the  Earth. 

3.  1304  :  17-18.  The  Earth's  Interior. 

4.  1601 : 16.  The  Earth  Cooled  by  Water. 

a.  1001 :  66.  Constitution  of  the  Earth's  Interior. 

6.  1207 :  88-90.  The  Result  of  the  Cooling  of  the  Earth's 
Interior. 

c.  1302  :  28-29.  Temperature  of  the  Center  of  the  Earth. 

d.  1303  :  16-17.  Underground  Temperatures. 

e.  1305  :  41-42.  Interior  of  the  Earth  and  its  Crust. 
/.  1306  :  11-12.  Temperature  of  the  Earth. 

g.    1306 :  205-206.    Interior  Condition  of  the  Earth. 

h.   1309  :  40-45.       Evidences  of  Internal  Heat. 

i.    1311 :  4.  The  Earth  Within  and  Without. 


68  INTRODUCTION  TO  GENERAL  SCIENCE 

49.    DIRECTION  —  LATITUDE  AND  LONGITUDE 

When  people  began  to  travel  over  the  seas,  it  became  nec- 
essary to  locate  places  on  the  earth's  surface.  Since  the 
earth  approaches  the  sphere  in  shape,  any  section  of  it  being 
almost  a  circle,  the  system  which  had  been  used  to  measure 
rotary  motion  was  adapted  to  this  purpose.  A  starting  point 
was  required  for  the  north  and  south  directions,  and  another 
for  east  and  west.  Nature  supplied  one,  man  the  other. 

Since  the  equator  is  halfway  between  the  north  pole  and 
the  south  pole,  it  was  taken  as  the  starting  point,  and  latitude 
is  given  in  degrees,  minutes,  and  seconds,  north  or  south.  It 
made  no  difference  where  the  other  starting  point  was  taken, 
so  the  observatory  at  Greenwich  was  called  zero,  and  we  now 
speak  of  the  degrees,  minutes,  and  seconds,  east  or  west  from 
Greenwich.  Since  the  distance  from  the  equator  to  either 
pole  is  one  fourth  of  the  distance  around  the  earth,  their 
latitude  is  90°  north  or  south.  As  there  are  360°  in  a  circle 
any  longitude  more  than  180°  east  becomes  west.  Therefore 
180°  is  the  limit  of  eastward  or  westward  distance  from  Green- 
wich. 

The  north  can  be  located,  very  nearly,  at  night  by  the 
North  Star,  and  in  the  daytime  by  means  of  the  sun  at  real 
noontime.  This  occurs  when  an  object  casts  the  shortest 
shadow.  The  North  Star  is  located  by  means  of  the 
"  pointers  "  of  the  "  Dipper."  Consult  the  references  for 
details. 

References :  — 

1.  1002:27-28.  The  Geographical  System. 

2.  1304 :  7.  The  Location  of  the  North  Star. 

3.  1304 :  402-405.  Latitude  and  Longitude. 

a.    1302  : 13-14.         Location  of  the  North  Star. 


MOTIONS  OF   THE  EARTH  69 

6.    1303:8-11.  Latitude  and  Longitude. 

c.  1305 :  297-299.  Effect  of  Latitude  on  Climate. 

d.  1308:  100-101.  Effect  of  Latitude  on  Climate. 

e.  1310:311-313.  Latitude  and  Longitude. 

/.    1312  :  24-28.        Localization  of  Places,  —  Longitude  and 
Latitude. 

Experiment  23.  —  To  Locate  the  North  by  Means  of  the 
Sun. 

Apparatus:  Straight  stick,  string. 

a.  Tie  a  stone  to  the  string  and  use  it  as  a  plumb  bob. 
Drive  the  stick  into  the  ground  so  that  it  is  vertical,  using 
your  plumb  bob  to  test  your  work.  At  twenty  minutes  be- 
fore noon  begin  marking  where  the  end  of  the  shadow  falls. 
Repeat  every  three  minutes  until  the  shadow  begins  to 
lengthen.  A  line  from  the  stick  to  the  mark,  which  indicates 
the  shortest  shadow,  points  north.  This  shadow  is  cast  at 
real  noon.  See  Section  51,  Time. 

Experiment  24.  —  To  Locate  the  South  by  Means  of  a 
Watch. 

At  any  time  of  day  point  the  hour  hand  of  the  watch  at  the 
sun.  Halfway  between  the  hour  hand  and  the  figure  twelve, 
on  the  watch  dial,  is  the  south.  Repeat  at  different  times  of 
day  and  satisfy  yourself  that  this  method  is  correct.  Explain 
why  this  method  is  correct. 

50.    MOTIONS  OF  THE  EARTH 

The  earth  rotates  on  its  axis  once  in  about  twenty-four 
hours,  and  revolves  around  the  sun  once  a  year.  A  point  on 
the  equator  moves  about  one  thousand  miles  an  hour,  while 
the  whole  earth  moves  around  the  sun  at  the  rate  of  eighteen 
and  five-tenths  miles  a  second. 


70  INTRODUCTION  TO  GENERAL  SCIENCE 

The  proof  that  the  earth  revolves  on  its  axis  has  been  rather 
difficult,  and  would  have  been  impossible,  if  it  had  not  been 
for  unlimited  travel  combined  with  scientific  investigation. 
Since  the  poles  are  nearer  the  center  of  the  earth,  a  body  would 
weigh  more  at  the  poles  than  it  does  at  the  equator  on  account 
of  universal  gravitation.  It  has  been  computed  that  a  body 
would  weigh  -5-5-5-  more  at  the  poles  than  it  would  at  the 
equator.  It  has  been  discovered,  by  experiment,  that  a  body 
does  weigh  y^  more  at  the  poles  than  it  does  at  the  equator. 
This  is  the  best  proof  that  the  world  is  in  rotation.  If  you 
take  a  stone  and  tie  it  to  a  string  and  whirl  it  rapidly,  the 
stone  pulls  on  the  string.  In  the  same  way  a  body  at  the 
equator,  which  is  moving  at  the  rate  of  nearly  one  thousand 
miles  per  hour,  is  thrown  out  from  the  earth  with  a  force 
which  resists  the  weight  by  2^9-.  Near  the  poles  this  rotation 
is  very  slow,  just  as  the  hub  of  a  wheel  revolves  more  slowly 
than  the  rim,  and  a  body  is  not  thrown  out  with  the  same 
force,  that  is,  the  force  is  -g-gr  less.  Thus  it  is  evident  that 
the  earth  revolves,  since  p^  —  5^-5  =  ^b-- 

Revolution  around  the  sun  causes  seasons.  If  the  axis  of 
the  earth  were  not  inclined  to  the  plane  in  which  it  revolves 
around  the  sun,  seasons  would  be  unknown;  but  the  axis  of  the 
earth  is  inclined  23J°  to  what  is  called  the  plane  of  the  earth's 
orbit.  This  axis  always  points  in  one  direction  —  towards 
the  North  Star.  Thus  sometimes  the  north  end  of  the  earth 
is  turned  toward  the  sun ;  at  other  times  the  south  end  of  the 
earth's  axis  is  turned  toward  the  sun.  Therefore  the  sun  ap- 
parently moves  23  J°  north  of  the  equator  in  the  summer  time, 
and  23 1°  south  of  the  equator  in  the  winter  time. 
References :  — 

1.  1002 :  147-152.     Proofs  of  the  Rotation  of  the  Earth. 

2.  1002 : 168-172.     Proofs  of  the  Revolution  of  the  Earth. 


TIME 


71 


3.  1002:177-180. 

4.  1304:6-8. 

a.    1001 : 47-50. 
6.    1001:70-71. 

c.  1003:32-44. 

d.  1301:13-17. 

e.  1301:66-68. 
/.    1302 :  17-19. 
g.    1303:6-7. 
h.   1305:43-44. 
i.    1305:51-52. 
j.    1307:18-19. 
k.   1309:25-28. 

I.    1310:308-311. 
m.  1311 :  19-26. 
n.   1312 : 19-24. 


The  Seasons. 

Motions  of  the  Earth. 

Effects  of  the  Rotation  of  the  Earth. 

The  Earth's  Orbit. 

The  Revolution  of  the  Earth  round  the  Sun. 

Rotation,  Revolution,  and  their  Effects. 

Effects  of  Rotation  and  Revolution. 

Rotation  and  Revolution  of  the  Earth. 

Rotation  of  the  Earth  and  its  Consequence. 

Motions  of  the  Earth. 

Days,  Nights,  and  Seasons. 

Effects  of  Rotation. 

Rotation  and  Revolution  and  their  Effects. 

Rotation  and  Revolution  of  the  Earth. 

The  Year,  Day,  and  Night. 

Revolution  and  Rotation  and  their  Effects. 


51.    TIME 

The  motions  of  the  earth  furnish  the  natural  divisions  of 
time  —  day  and  night,  and  the  year.  One  complete  turning 
of  the  earth  on  its  axis  causes  day  and  night,  while  the  trip 
around  the  sun  results  in  the  march  of  the  seasons.  See  Sec- 
tion 52  for  a  discussion  of  the  seasons  and  their  causes.  The 
revolution  of  the  moon  around  the  earth  gave  us  the  month, 
until  man  discovered  that  the  moon  made  more  nearly  thir- 
teen than  twelve  trips  per  year.  The  week  is  an  artificial 
division  of  time,  and  is  not  founded  upon  any  natural  cause. 

Since  the  earth  revolves  360°  in  twenty-four  hours,  it  moves 
at  the  rate  of  15°  an  hour.  Therefore  two  places  which  are 
15°  apart,  east  and  west,  have  a  difference  in  time  of  one  hour. 
This  led  to  considerable  trouble  when  railroads  and  the  tele- 
graph brought  places  nearer  together,  and  Standard  Time  was 
devised  to  prevent  misunderstandings. 


72         INTRODUCTION  TO  GENERAL  SCIENCE 

The  United  States  is  divided  into  four  time  belts,  each  15° 
wide,  and  each  belt  takes  the  time  of  its  center  meridian  for 
all  parts  of  the  belt.  This  makes  the  maximum  difference 
between  standard  time  and  local  time  one  half  an  hour. 
Local  time  is  not  used  except  in  astronomy. 

References:  — 

1.  1002:226-242,  Time. 

2.  1304 :  404-405.  Longitude  and  Time. 

3.  1803  :  5.  The  Standard  Unit  of  Time. 

a.  1001 :  33-36.  Different  Kinds  of  Time. 

b.  1001 :  36-41.  Determination  of  Time. 

c.  1003:48-55.  Time. 

d.  1309 :  28.  Sidereal  and  Solar  Days  —  Standard  Time. 

e.  1310 :  313-314.  Longitude  and  Time. 
/.  1311:26-27.  Time. 

g.   1312 : 30-32.        The  Day  —  Standard  Time. 

52.    THE  SEASONS 

Every  one  is  familiar  with  the  change  of  seasons,  although 
perhaps  only  a  few  have  noticed  the  cause  of  the  changes. 
The  weather  is  warmer  in  summer  than  in  winter  for  the  same 
reason  that  there  is  a  higher  temperature  at  the  equator  than 
at  any  other  place  on  the  earth.  The  more  nearly  vertical 
the  rays  of  the  sun  are,  the  more  energy  is  received  per  square 
foot.  To  put  it  another  way, — the  more  nearly  the  sun  is 
overhead,  the  warmer  it  is,  at  the  surface  of  the  earth.  The 
reason  that  the  sun  appears  higher  in  the  sky  during  the 
summer  is  because  the  axis  of  the  earth  is  inclined  23  J°  to  its 
path  around  the  sun.  Since  the  north  end  of  the  axis  always 
points  in  one  direction, — to  the  North  Star, — the  sun  seems 
to  mount  higher  in  the  sky  when  the  earth  is  in  such  a  position 
that  its  axis  points  the  north  end  in  the  general  direction  of 


THE  SEASONS  73 

the  sun.  In  winter  time  the  north  end  of  the  axis  is  turned 
away  from  the  sun,  and  the  latter  appears  lower  in  the  sky,  or, 
in  other  words,  in  a  very  northern  locality,  the  sun  may  not 
rise  above  the  horizon. 

References :  — 

1.  1002 : 177-180.         The  Cause  of  Seasons. 

2.  1103  :  40-42.  Temperature  Changes  during  the  Revolu- 

tion of  the  Earth. 

3.  1304  :  397-401.          The  Cause  of  Seasons  Explained. 
a.    1004 :  95-99.         The  Seasons. 

6.  1302  :  19-22.  The  Change  of  Seasons. 

c.  1303  :  46-49.  Seasons  and  Zones. 

d.  1305  :  52-53.  The  Seasons. 

e.  1309  :  29-31.  The  Change  of  Seasons. 
/.  1310 :  341-346.  The  Seasons. 

g.    1311:  20-26.         The  Motions  of  the  Earth  and  the  Seasons. 
h.    1312:23-24,        The  Seasons. 

Experiment  25. — The  Seasons — Length  of  Day  and  Night. 

Apparatus :  A  small  globe. 

a.  Place  the  globe  so  that  it  receives  light  from  a  window, 
or  from  some  artificial  light  at  least  ten  feet  distant.  Turn 
the  globe  so  that  the  north  end  of  its  axis  points  at  right 
angles  to  an  imaginary  line  drawn  from  the  globe  to  the 
source  of  light.  How  much  of  the  whole  globe  is  illuminated  ? 
How  much  of  the  equator  ?  How  much  of  the  sixtieth  parallel 
of  latitude? 

6.  Turn  the  axis  of  the  globe  so  that  it  points  in  the  general 
direction  of  the  window.  How  much  of  the  whole  globe  is  illu- 
minated ?  How  much  of  the  equator  ?  How  much  of  the  thir- 
tieth parallel  ?  How  much  of  the  sixty-sixth  parallel  ?  Since 
the  illuminated  part  indicates  day,  what  is  the  length  of  day 
and  night  in  each  latitude  ?  (Count  the  meridians  of  latitude.) 


74  INTRODUCTION  TO  GENERAL  SCIENCE 

c.  Turn  the  globe  so  that  the  north  end  of  the  axis  points 
away  from  the  source  of  light  and  answer  the  same  questions 
as  in  (6). 

d.  What  season  is  represented  by  (a),  (&),  and  (c),  respec- 
tively?    Does  the  length  of  day  vary  at  the  equator? 

53.    THE  CALENDAR 

Upon  the  rotation  and  revolution  of  the  earth  is  based  our 
calendar,  or  record  of  time.  There  have  been  a  great  many 
changes  in  the  calendar  since  man  first  tried  to  reckon  time. 
Much  has  been  discovered  concerning  the  exact  time  of  the 
rotation  of  the  earth,  and  its  revolution  around  the  sun,  and 
the  calendar  has  been  altered  to  meet  known  conditions. 
Time  has  been  reckoned  by  the  moon,  but  more  generally  by 
the  seasons,  and  by  day  and  night.  The  Julian  Calendar, 
prepared  by  learned  men  at  the  direction  of  Julius  Caesar; 
was  in  force  until  1582,  when  it  was  found  to  be  ten  days  be- 
hind time.  Pope  Gregory  caused  this  time  to  be  dropped 
and  the  calendar  brought  up  to  date,  and  ordered  that  every 
fourth  year  should  have  an  extra  day.  This  was  called  the 
Gregorian  Calendar.  This  calendar  is  not  exactly  correct, 
but  by  the  method  of  omitting  the  leap  year  at  the  end  of  each 
century,  except  those  centuries  that  are  divisible  by  four  hun- 
dred, the  calendar  will  be  nearly  correct. 

References :  — 

1.  1002  :  240-241.  The  Calendar. 

2.  1304  :  7-8.  Effects  of  Revolution  and  Rotation. 
a.    1001  :  85-87.  The  Calendar. 

6.  1003  :  133-136.  The  Calendar. 

c.  1004  :  101-104.  The  Year  and  the  Calendar 

d.  1303  :  7-8.  Day  and  Night :  a  Natural  Unit  of  Time. 

e.  1309  :  28-29.  The  Calendar  and  Time. 
/.  1312 :  29-32.  The  Calendar  and  Time. 


THE   MOON  75 

54.    THE  MOON 

The  nearest  heavenly  body,  which  arouses  our  curiosity 
more  than  other  bodies  on  account  of  its  apparent  size,  is  our 
one  satellite,  the  moon.  It  is  quite  probable  that  the  moon 
was  once  part  of  the  earth,  while  the  crust  of  the  earth  was 
still  very  thin.  Perhaps  the  earth  was  of  irregular  shape,  and 
the  moon  was  one  of  the  large  irregularities,  and  was  thus 
thrown  off,  something  like  mud  from  the  tire  of  a  wheel.  The 
moon  shines 'by  reflected  light,  and  since  the  relation  and 
position  of  the  earth,  moon,  and  sun  are  constantly  changing, 
part  of  the  moon  is  in  shadow  and  part  in  light,  and  we  see 
its  different  phases.  The  moon  revolves  around  the  earth 
every  twenty-seven  and  one-third  days,  and  also  rotates  on 
its  axis  in  the  same  time.  Thus  we  have  never  seen  but  one 
side  of  the  moon. 

The  moon  is  now  cold  and  has  practically  no  water  on  it. 
Therefore  it  has  no  vegetation,  and  we  have  an  example  of  a 
dead  planet;  for,  in  essential  respects,  the  moon  has  every 
characteristic  of  a  planet.  The  surface  of  the  moon  shows 
the  result  of  vast  volcanic  action,  which  proves  that  the  moon 
once  was  hot,  but  gradually  lost  all  its  heat. 

References :  — 

1.  1002 :  247-249.  The  Moon's  Phases. 

2.  1002  :  251-254.  •  Distance,  Orbit,  Rotation  of  the  Moon. 

3.  1002 :  254-260.  Size,  Mass,  Density,  Atmosphere,  of  the 

Moon. 

4.  1002  :  264-268.  General  Surface  Conditions  of  the  Moon. 

5.  1002  :  271.  Effects  of  Moon  on  the  Earth, 
a.    1001 :  88.  The  Moon. 

6.    1001 :  93-94.        The  Moon's  Distance. 

c.  1001 :  97-98.         Diameter,  Mass,  Rotation,  of  the  Moon. 

d.  1001 : 103-110.     The  Physical  Characteristics  of  the  Moon. 


76  INTRODUCTION  TO  GENERAL  SCIENCE 

e.  1003  :  112-132.      The  Moon,  Tides,  and  Eclipses. 

/.  1004:  117-125.      Physical  Characteristics  of  the  Moon. 

g.  1306  :  13-15.         The  Moon,  Tides,  and  Eclipses. 


55.    TIDES 

The  chief  effect  of  the  moon  upon  the  earth  is  the  produc- 
tion of  tides  in  the  ocean.  The  earth  and  the  moon  are  at- 
tracted each  by  the  other,  but  since  the  water  is  more  mobile 
than  the  solid  earth,  the  ocean  piles  up  on  the  side  nearest  the 
moon  and  forms  what  is  called  high  tides.  These  tides,  out 
in  the  ocean,  are  about  four  feet  above  mean  sea  level.  Near 
the  shore  tides  may  be  much  higher  on  account  of  the  shape 
of  the  bays.  Not  only  is  there  a  high  tide  nearest  the  moon, 
but  there  is  another  on  the  side  of  the  earth  opposite  to  the 
moon,  and  in  between  these  two  tides  are  two  low  tides,  on 
opposite  sides  of  the  earth.  In  a  general  way,  the  explana- 
tion is  as  follows:  Since  the  water  on  the  side  of  the  earth 
farther  away  from  the  moon  is  not  attracted  as  strongly  as  the 
earth  is,  the  latter  is  pulled  away  from  the  water,  leaving  the 
water  apparently  high.  The  scientific  explanation  of  tides 
belongs  properly  to  advanced  physics. 

The  sun  also  produces  tides  on  the  earth  which  are  very 
slight  compared  with  the  moon's  tides.  However,  if  both  the 
sun  and  the  moon  are  on  the  same  side,  or  opposite  sides,  of 
the  earth,  the  result  is  that  both  act  together  to  produce  an 
extra  high  tide.  These  tides,  which  occur  about  twice  a  month, 
are  called  spring  tides.  If  a  line  from  the  moon  to  the  earth 
forms  approximately  a  right  angle  with  a  line  from  the  earth 
to  the  sun,  the  effect  of  th£  sun  on  the  water  is  to  reduce  the 
moon  tides  slightly;  these  tides,  which  also  occur  about  twice 
a  month,  are  called  neap  tides. 


METEORS  77 

References :  — 

1.  1002  :  220-221.          Variation  in  the  Tides. 

2.  1304 :  187-189.          Tides. 

a.  1001 :  187-198.  Tides  and  their  Effects. 

6.  1301 :  210-214.  The  Tides  and  their  Causes. 

c.  1303  :  124-126.  The  Cause  of  Tides. 

d.  1305  :  125-134.  Tides,  their  Causes  and  Variations. 

e.  1306:192-203.  Tides. 
/.  1307:201-204.  Tides. 

g.    1308  :  10-15.  Tides  and  Tidal  Currents. 

h.   1309:183-192.  Tides. 

i.   1311 :  290-295.  Tides  and  their  Causes. 

j.   1312 : 181-184.  Tides,  Tidal  Waves,  and  their  Causes. 

k.    1313:111-113.  Tides. 

56.    METEORS 

These  are  very  small  bodies  of  matter,  or  combinations  of 
small  bodies,  revolving  around  the  sun  like  the  planets.  They 
are  cold,  and  not  large  enough  to  reflect  sufficient  light  to  be 
seen,  and  therefore  they  are  invisible  until  they  suddenly 
flash  into  our  atmosphere.  The  light  is  produced  by  the  in- 
tense heat  due  to  friction  against  our  atmosphere.  The  large 
majority  of  meteors  are  entirely  consumed,  or  dissipated  into 
dust,  before  they  reach  the  earth.  A  huge  number  of  meteors 
fall  every  year,  and  it  has  been  estimated  that  they  add  about 
forty  thousand  tons  of  weight  to  the  earth  each  year.  As 
they  fall  to  the  earth  they  move  at  about  twenty-six  miles  a 
second,  and  their  fall  may  be  accompanied  by  a  roaring  noise 
and  often  ends  in  an  explosion.  Their  composition  is  mostly 
stone,  although  some  have  been  found  composed  practically 
of  pure  iron. 

References :  — 

1.  1002  :  374-381.  Meteors  and  Meteorites. 

2.  1002 :  384-385.          Theories  Respecting  Origin  of  Meteorites. 


78 


INTRODUCTION   TO  GENERAL  SCIENCE 


a.  1001  : 289-299. 

6.  1003:187-190. 

c.  1004:279-283. 

d.  1004:283. 

e.  1004:290-293. 

/.  1303:23. 

g.  1305:37-38. 

h.  1306:15-17. 

i.  1310:324-325. 

j.  1312:10. 


Meteors  and  Shooting  Stars. 

Meteors  and  Meteoric  Showers. 

Meteors  and  Shooting  Stars. 

Light,  Heat,  and  Origin  of  Meteors  and 

Shooting  Stars. 
The     Connection    between    Comets    and 

Meteors. 

Meteors  or  "Falling  Stars." 
Meteors  and  Comets. 
Comets,  Shooting  Stars,  and  Meteors. 
Height  of  Atmosphere  Shown  by  Meteors. 
Meteors  and  Shooting  Stars. 


57.    COMETS 

Comets  are  composed  of  a  head  or  nucleus,  and  a  tail  which 
varies  in  length,  increasing  as  the  comet  approaches  the  sun. 
The  volume  of  a  comet  is  extremely  large,  almost  passing 
human  comprehension.  Yet  the  mass  is  very  slight,  and  in 
the  largest  comet  is  only  a  small  fraction  of  the  earth's  mass. 
The  light  of  a  comet  is  due  partly  to  light  reflected  from  the 
sun,  and  partly  to  some  electrical  disturbance  which  is  not 
well  understood.  They  are  composed,  doubtless,  of  large 
aggregations  of  very  small  meteors  acting  as  one  large  body. 
It  is  probable  that  if  the  earth  were  struck  by  a  comet,  the 
shock  of  collision  would  be  very  slight  and  little  damage 
would  be  done. 


References :  — 

1.  1002:356-371. 

2.  1002:381. 

a.    1001:264-289. 

6.    1001:381. 

c.    1001:299-302. 


Comets  and  Meteors. 
Connection  between  Comets  and  Meteors. 
Comets. 

Danger  from  Comets. 
The    Connection    between    Comets    and 
Meteors. 


THE  STARS  79 

d.  1003  :  176-180.     Comets  and  Meteors. 

e.  1003:185-187.-    Constitution  of  Comets. 

/.  1004 :  261-266.  Mass  and  Density  of  Comets. 

g.  1004  :  267-271.  The  Tails  of  Comets. 

h.  1004:271.  Nature    of    Comets    and    Danger    from 

Comets. 

i.  1004 :  290-293.  Relation  between  Comets  and  Meteors. 

j.  1305:37.  Comets. 

k.  1312:8-10.  Comets. 


58.    THE  STARS 

Only  an  estimate  can  be  made  in  regard  to  the  number  of 
stars,  but  approximately  five  thousand  are  visible  to  the 
naked  eye,  while  probably  more  than  one  hundred  million  can 
be  identified  with  the  modern  astronomical  instruments.  We 
must  remember,  too,  that  all  the  stars  are  suns,  and  that  it  is 
quite  likely  that  some  suns  have  their  planets  revolving 
around  them,  which  are  too  small  to  be  seen. 

References :  — 

1.  1002  :  52.  The  Number  of  Stars. 

2.  1304  :  3-4.  Other  Spheres. 

a.  1001:303-304.  The  Number  of  Stars. 

6.  1001 :  341.  Planetary  System  Attending  Stars. 

c.  1003  :  191-192.  About  Stars  in  General. 

d.  1004:294-295.  Number  of  Stars. 

e.  1004 :  310-311.  Dimensions  of  the  Stars. 
/.  1301:25-27.  The  Universe. 

g.    1302  :  13-14.  The  Starry  Heavens. 

h.    1303  :  14.  The  Stars  Resemble  the  Sun. 

i.    1305  :  35.  Fixed  Stars  and  Planets. 

j.    1306 :  17-18.  The  Stellar  System. 

k.   1309 : 14.  The  Sun  is  also  a  Star. 


80  INTRODUCTION  TO  GENERAL  SCIENCE 


59.    DISTANCES  OF  THE  STARS 

The  stars  are  so  distant  that  we  must  make  use  of  a  unit  of 
measurement  other  than  the  mile.  It  would  be  hard  to  ex- 
press these  distances  in  miles,  and  the  numbers  would  be 
meaningless.  Light  travels  one  hundred  and  eighty-six  thou- 
sand miles  a  second.  The  unit  of  distance  is  taken  as  the 
space  through  which  light  would  pass  in  one  year,  which  is 
called  the  light-year.  Using  this  standard  of  measurement, 
the  nearest  star  is  about  three  light-years  away.  Those  stars 
which  are  just  visible  to  the  naked  eye  are  between  two  hun- 
dred and  three  hundred  light  years  distant.  The  telescopic 
stars,  that  is,  those  stars  which  can  be  seen  only  through  the 
telescope,  are  so  distant  that  the  light  from  them  has  been 
thousands  of  years  on  its  way  to  us.  When  we  see  some  change 
in  a  star,  or  group  of  stars,  we  are  seeing  something  which 
happened  several  hundreds  of  years  ago. 

References :  — 

1.  1002  :  504-507.  Distances  of  the  Stars. 

2.  1803  :  390.  Results  of  the  Finite  Speed  of  Light, 
a.   1001 :  315.  The  Unit  of  Stellar  Distance. 

6.  1003  :  209-212.  Distances  of  the  Stars. 

c.  1004  :  304-306.  Distance  of  the  Stars  —  The  Light- Year. 

d.  1301 :  27.  Distances  of  the  Stars. 

e.  1303 : 12.  Distances  of  the  Stars. 


60.    THE  EARTH  AS  A  WHOLE 

The  surface  of  the  earth  is  a  solid  mass  of  rock,  of  which 
only  a  very  thin  top  layer  has  been  changed  to  soil  and  sand. 
Thus  the  surface  is  covered  in  most  places,  except  where  the 
rocks  show  through,  with  a  mixture  of  material  ranging  in 


THE  EARTH  AS  A   MAGNET  81 

size  and  bulk  from  bowlders  to  clay.  The  interior  of  the  earth 
is  probably  solid  rock,  although  hot  enough  to  be  liquid,  if  it 
were  not  for  the  pressure  upon  it. 

References :  — 

1.  1002:114-119.  Shape  of  the  Earth. 

2.  1002  :  129-130.  Density  of  the  Earth. 

3.  1103  : 21-23.  Relation  of  the  Earth  to  the  Sun. 

4.  1304  :  13-28.  General  Features  of  the  Earth, 
a.    1001 :  45.  General  Features  of  the  Earth. 
6.    1004 :  78-88.  General  Features  of  the  Earth. 

c.  1302  :  26-29.  Structure  of  the  Earth. 

d.  1302  :  29-33.  The  Earth's  Crust  —  Mantle  Rock. 

e.  1303  :  15-17.  Structure  and  Temperature  of  Earth. 
/.  1305  :  41-42.  Internal  Condition  of  the  Earth. 

g.  1309  :  18-22.  Shape,  Size,  and  Density  of  the  Earth. 

h.  1310 :  307-308.  Form  of  the  Earth. 

i.  1311 :  1-12.  Changes  on  the  Earth. 

j.  1312 : 16-19.  Shape,  Size,  and  Structure  of  the  Earth. 


61.    THE  EARTH  AS  A  MAGNET 

The  ordinary  magnet  is  a  piece  of  hardened  steel,  which, 
having  been  rubbed  by  another  magnet,  or  influenced  by  an 
electric  current,  is  capable  of  attracting  pieces  of  iron  or  steel. 
If  we  suspend  such  a  magnet  by  a  fine  thread,  or  on  a  delicate 
pivot,  we  will  find  that  it  takes  a  definite  direction,  the  ends 
pointing  north  and  south.  This  is  due  to  the  magnetism  of 
the  earth. 

The  points  toward  which  the  needle  directs  itself  are  called 
the  magnetic  north  and  south  poles,  but  they  do  not  lie  at  the 
geographical  north  and  south  poles.  Thus,  if  we  go  east  or 
west,  there  will  be  a  decrease  or  increase  in  the  variation  be- 
tween the  true  north  and  the  north  which  is  indicated  by  the 

G 


82  INTRODUCTION  TO  GENERAL   SCIENCE 

magnetic  needle.     This  variation  is  not  always  constant,  as 
the  magnetic  poles  swing  backward  and  forward. 

The  cause  of  the  earth's  magnetism  is  not  fully  understood, 
but  it  is  probably  due  to  the  energy  which  the  earth  receives 
from  the  sun.  If  there  is  any  disturbance  of  the  sun,  as  when 
sun  spots  appear,  there  is  always  a  disturbance  of  all  the  mag- 
netic needles  on  the  earth.  Under  these  conditions  the  needles 
act  as  if  the  magnetic  poles  were  swinging  hundreds  of  miles. 

References :  — 

1.  1002  :  437-438.  A  Theory  of  the  Earth's  Magnetism. 

2.  1304:418-419.  .    Magnetism. 

3.  1803  :  235-237.  Terrestrial  Magnetism. 
a.    1303  :  17-18.  The  Earth  as  a  Magnet. 

6.  1305  :  30-33.  The  Earth  a  Huge  Magnet. 

c.  1306  :  29-30.  Magnetism  and  Electricity. 

d.  1307  :  274-279.  The  Aurora  and  the  Earth's  Magnetism. 

e.  1307  :  279.  Magnetic  Storms. 

/.  1309:33-39.  The  Earth  as  a  Magnet  and  Magnetic 

Storms. 

fir.  1310 :  301-305.  Terrestrial  Magnetism. 

h.  1311 :  274-278.  The  Earth's  Magnetism. 

i.  1312  :  33.  The  Earth  as  a  Magnet. 

j.  1809  :  367-369.  Terrestrial  Magnetism. 

k.  1810 :  245-246.  The  Earth  a  Magnet. 

Experiment  26.  —  The  Earth's  Magnetism. 

Apparatus :  Bar  magnet,  pieces  of  steel,  clock  spring  at  least 
3"  long,  wooden  support,  very  fine  silk  thread,  or  untwisted 
fiber. 

a.  Support  a  piece  of  clock  spring  at  its  middle  point  by  a 
thread  at  least  12"  long,  and  slowly  bring  one  end  of  the  magnet 
near  it.  Do  not  touch  the  piece  of  clock  spring  with  the  mag- 
net. If  you  happen  to,  ask  for  another  piece.  Approach  the 


OTHER  MAGNETS  83 

other  end  of  the  magnet  to  the  clock  spring.     You  should  not 
see  any  difference  in  the  result. 

b.  Touch  one  end  of  the  clock  spring  to  one  end  of  the  mag- 
net, and  then  touch  the  other  end  of  the  clock  spring  to  the 
other  end  of  the  magnet.     This  magnetizes  the  clock  spring. 
Support  the  clock  spring  as  before,  and  repeat  (a).     Do  this 
several  times  and  make  a  complete  statement  of  your  ob- 
servations. 

c.  Remove  all  magnets  and  iron  from  near  the  clock  spring 
and  it  will  take  a  definite  direction  due  to  the  earth's  mag- 
netism.    How  does  this  compare  with  the  direction  of  the 
true  north? 

62.    OTHER  MAGNETS 

Besides  the  earth,  there  are  other  magnets,  some  natural 
and  some  which  are  made  by  man.  A  certain  ore  of  iron, 
called  magnetite,  on  account  of  its  peculiarity,  has  a  weak 
attraction  for  iron  and  steel.  Suitable  pieces  of  this  ore  are 
sometimes  mounted  with  iron  ends,  and  are  capable  of  holding 
up  a  mass  of  iron  which  is  equal  to  their  own  weight.  Power- 
ful magnets  are  made  from  steel  bars  which  have  received  their 
magnetism  through  the  agency  of  electricity.  If  a  wire  covered 
with  cotton,  silk,  or  some  other  material  through  which  elec- 
tricity does  not  readily  pass,  is  wound  around  a  piece  of  iron, 
and  a  current  of  electricity  allowed  to  pass  through  the  wire, 
the  iron  will  become  a  strong  magnet,  attracting  other  pieces 
of  iron  and  steel  with  considerable  force.  As  soon  as  the 
electricity  ceases  to  pass  through  the  wire  around  the  iron, 
the  iron  loses  its  magnetism.  If,  on  the  other  hand,  a  simi- 
lar electric  current  is  passed  around  steel,  the  magnetism 
remains  in  the  steel,  after  the  electric  current  has  been  dis- 
continued. Therefore  a  steel  magnet  is  called  permanent. 


84  INTRODUCTION  TO  GENERAL  SCIENCE 

The  reason  that  electricity  produces  magnetism  in  a  piece  of 
iron  is  because  there  is  magnetism  around  every  wire  carry- 
ing an  electric  current.  Magnetism  is  induced  in  the  iron. 
This  effect  is  made  use  of  in  the  electromagnet,  bell,  tele- 
phone, telegraph,  motor,  and  dynamo,  as  well  as  in  many 
toys. 
References :  — 

1.  1803:227-234.  Magnetism. 

2.  1803:261-262.          Electricity    in    Motion    Produces   Mag- 

netism. 

a.  1801 :  300-310.  Magnetism. 

6.  1802 :  368-378.  Magnetic  Effect  of  the  Electric  Current. 

c.  1804:523-530.  Magnetism. 

d.  1805:369-380.  Magnetism. 

e.  1806:429-439.  Magnetism. 
/.  1807:339-352.  Magnetism. 
g.  1808:248-264.  Magnetism. 
h.  1809  :  359-373.  Magnetism. 

Experiment  27.  —  Magnetism. 

Apparatus :  Two  bar  magnets  six  inches  long,  piece  of  quar- 
ter-inch iron  rod  (large  nail),  thirty  feet  of  double  cotton- 
covered  copper  wire  No.  20,  dry  cell,  bits  of  wood,  brass,  iron 
nail,  silk  thread. 

a.  Suspend  one  magnet  at  its  middle  point  by  a  silk  thread, 
and  balance  it.     If  the  thread  is  allowed  to  untwist,  the  mag- 
net may  point  to  the  north.     Approach  in  succession  the  two 
ends  of  the  other  magnet.     The  similar  poles  are  marked. 
Write  out  the  laws  of    attraction  and  repulsion.     Do  the 
magnets  have  to  obey  these  laws  ? 

b.  Wind  about  thirty  feet  of  insulated  wire  on  the  large 
nail,  trying  to  imitate  the  winding  of  thread  upon  a  spool. 
Note  that  there  is  no  magnetism  in  the  iron.     Attach  the  two 
ends  of  the  wire  to  the  connecting  screws  of  the  dry  cell.     Can 


THE  NORTHERN  LIGHTS  '85 

the  electromagnet  pick  up  iron  now  ?  Can  it  pick  up  any- 
thing except  iron  and  steel  ?  Disconnect  the  dry  cell.  Is  the 
nail  a  magnet  now  ?  Note  :  Do  not  leave  dry  cell  attached  to 
magnet  for  more  than  a  few  seconds  at  a  time,  or  the  dry  cell 
will  be  spoiled. 

c.  Approach  the  electromagnet  to  the  suspended  magnet. 
Has  it  two  poles  ?  Change  the  connection  of  the  dry  cell  and 
test  the  electromagnet  by  the  suspended  magnet.  What 
has  happened?  Electricity  is  reversible,  and  magnetism 
likewise. 

63.    THE  NORTHERN  LIGHTS 

At  night  in  the  far  north  the  northern  sky  is  often  illumi- 
nated with  beautiful  fluttering  streamers  of  colored  light  which 
now  grow  brighter,  now  dimmer;  often  changing  in  color, 
they  are  ever  glorious.  At  the  same  time  that  these  wonder- 
ful displays  take  place,  the  magnetic  needles  quiver  and  jump, 
showing  that  there  is  some  connection  between  the  Northern 
Lights  and  the  earth's  magnetism.  A  theory  which  is  rapidly 
gaining  in  favor  with  scientists  is  that  the  magnetism  of  the 
earth  and  the  Northern  Lights  both  owe  their  origin  to  the 
electrical  energy  which  the  earth  is  receiving  from  the  sun. 
Since  sun  spots  influence  the  magnetic  needle,  the  relation 
seems  to  be  reasonable.  Electrical  discharges  through  rare- 
fied gases  produce,  in  a  small  way,  the  same  color  effects  as  are 
manifested  in  the  Northern  Lights. 

References :  — 

1.  1002:139.  The  Aurora. 

2.  1103  :  175-176.  The  Aurora  and  its  Cause. 

3.  1304  :  419.  The  Aurora  Borealis  and  Australis. 
a.    1102  :  270-271.  The  Aurora  Borealis. 

6.    1303:18-19.        The  Aurora, 


86  INTRODUCTION   TO  GENERAL  SCIENCE 

c.  1305:108.  The  Aurora. 

d.  1309 :  277-278.  The  Aurora  and  its  Cause. 

e.  1312 :  396-397.  The  Aurora  and  its  Cause. 
/.   1801:336.  The  Aurora. 

64.    SOURCES  OF  ELECTRICITY 

There  are  three  sources  of  electricity  —  frictional,  chemi- 
cal, and  magnetic.  The  quantity  of  electricity  produced  by 
friction  is  very  small.  Whenever  one  substance  is  rubbed  by 
another,  electricity  results  and  may  be  easily  detected.  Two 
pieces  of  lump  sugar,  if  rubbed  together  in  a  dark  place,  will 
give  out  slight  flashes  of  light.  It  is  possible  to  obtain  an 
electric  spark  from  a  cat,  by  rubbing  its  back  and  then  touch- 
ing its  nose  or  ear.  Put  the  cat  on  an  insulated  chair,  that 
is,  have  plates  of  glass  under  the  legs  of  the  chair. 

Whenever  two  dissimilar  elements  are  placed  in  a  suitable 
solution,  and  their  ends  joined,  a  current  of  electricity  passes 
which  varies  in  strength  according  to  the  elements  and  the 
solution.  Such  a  combination  is  called  a  galvanic  cell,  and 
modifications  of  these  cells  are  used  largely  for  electric  bells 
and  gas  ignition. 

By  far  the  greatest  amount  of  electricity  is  produced  by 
moving  a  wire  near  a  magnet.  If  such  a  wire  has  its  ends 
joined,  a  current  of  electricity  will  pass  through  it.  The  cause 
for  this  production  of  electricity  is  not  known.  The  dynamo 
is  the  practical  application  of  this  principle. 

References :  — 

1.  1103:175-179.  Atmospheric  Electricity. 

2.  1803  :  238-239.  Development  of  Electrification  by  Friction. 

3.  1803  :  262-263.  The  Galvanic  Cell. 

4.  1803 :  282-283.  The  Theory  of  the  Simple  Cell. 


SOURCES  OF  ELECTRICITY  87 

5.  1803  :  312.  The  Principle  of  the  Dynamo. 
a.    1801 :  312-314.     Electrification  by  Friction. 

6.  1801 :  337-340.  The  Simple  Voltaic  Cell. 

c.  1801:378-381.  Electromagnetic  Induction. 

d.  1804:434-435.  Electrification. 

e.  1804 :  465-468.  Voltaic  Cell. 

/.  1805  :  380-391.  The  Simple  Voltaic  Cell. 

g.  1805  :  430-437.  The  Electric  Dynamo. 

h:  1806 :  481-484.  Electrification  by  Friction. 

i.  1806 : 501-502.  Electricity  Developed  by  Chemical  Action. 

j.  1807:353-356.  Voltaic  Cell. 

k.  1807 :  389-404.  Electromagnetic  Induction. 

I.  1808 :  293-294.  The  Electric  Current. 

Experiment  28.  —  Sources  of  Electricity. 

Apparatus :  Pith  ball  on  stand,  rubber  rod,  dry  cell,  strips 
of  zinc  and  copper,  or  carbon,  glass  tumbler,  magnetic  needle, 
six-inch  magnet,  fifty  feet  insulated  copper  wire  No.  20. 

Materials :  Dilute  sulphuric  acid  (one  part  acid  to  nine  parts 
water) . 

a.  Bring  the  rubber  rod  near  the  pith  ball.  Nothing  hap- 
pens. Dry  the  rod,  rub  it,  and  bring  it  near  the  pith  ball. 
What  happens  ?  Let  the  pith  ball  touch  the  rubber  rod  and 
again  approach  the  rubber  rod.  Tell  what  happens,  and  give 
the  laws  of  electric  charges.  Note :  When  the  pith  ball 
touched  the  rod,  it  became  charged  with-  the  same  kind  of 
electricity.  Before  being  touched,  it  had  induced  in  it  the 
opposite  kind  of  electricity. 

6.  Wind  ten  feet  of  insulated  wire  around  the  compass  in  a 
thin  coil,  piling  some  of  the  windings  upon  others.     This 
makes  a  galvanometer,  and  to  use  it  the  coils  should  run  north 
and  south.     Attach  the  dry  cell  and  note  how  the  needle  turns. 
Reverse  the  connections  and  see  in  which  direction  the  needle 
turns.    Take  as  your  guide  that  the  electricity  comes  from  the 


88  INTRODUCTION  TO  GENERAL  SCIENCE 

carbon  of  the  dry  ceil  and  returns  to  the  cell  through  the  zinc. 
The  carbon  is  called  positive,  +,  and  the  zinc  negative,  — . 

c.  Take  a  strip  of  copper  and  one  of  zinc.     Attach  them  by 
wires  to  your  galvanometer  and  place  them  in  a  glass  tumbler. 
Pour  in  a  little  of  the  dilute  solution,  watching  the  needle  of 
the  compass.     What  happens?     In  what  direction  does  the 
needle  turn?   Which  is  +,  copper  or  zinc?   The  current  soon 
decreases  on  account  of  chemical  changes  taking  place  within 
the  solution  and  because  the  bubbles  of  hydrogen,  which  are 
set  free,  offer  resistance  to  the  flow  of  the  current.     Shake  the 
copper  strip,  and  watch  the  needle. 

d.  Wind  forty  feet  of  wire  around  the  magnet,  in  a  close 
coil,  after  first  winding  the  magnet  with  twenty  turns  of 
paper.     Remove  the  coil  and  pull  out  the  paper.     Attach  the 
coil  to  the  galvanometer  by  means  of  wires  which  are  at  least 
six  feet  long.     Now,  watching  the  needle,  push  one  end  of  the 
magnet  into  the  coil.     Note  deflection  of  needle.     Which 
way  did  the  current  go?    Where  did  the  electricity  come 
from?    Again  watching  needle,  remove  the  magnet.     Con- 
clusions?    Repeat  with  the  other  end  of  the  magnet.     Con- 
clusions? 

65.    APPLICATIONS  OF  ELECTRICITY 

In  this  section  we  shall  take  up  only  those  applications  of 
electricity  which  include  magnetism.  In  Sections  66  and  67 
other  applications  will  be  studied. 

Since  the  magnetism  by  electricity  lasts  only  while  the 
source  of  current  is  connected  with  the  magnetizing  coils,  we 
can  regulate  or  stop  and  start  the  magnetism  at  will.  The 
electric  bell  is  the  simplest  example.  The  electromagnet 
pulls  the  hammer  against  the  bell,  but  when  the  hammer  is 
nearly  there,  the  current  is  broken  by  means  of  the  spring 


APPLICATIONS  OF   ELECTRICITY  89 

connection  on  part  of  the  hammer,  and  the  latter  flies  back 
only  to  connect  the  electricity  and  be  attracted  again.  This 
continues  as  long  as  the  supply  of  electricity  lasts. 

The  electric  motor  consists  of  two  magnets,  one  stationary 
and  the  other  free  to  move  on  an  axis.  The  unlike  poles  at- 
tract each  other,  but  the  electricity  is  shut  off,  or  turned  into 
other  coils  of  the  moving  magnet,  just  before  it  comes  into  a 
position  of  equilibrium,  and  the  motion  continues. 

The  telegraph  is  nothing  but  an  electromagnet  and  a  mov- 
able piece  of  iron,  which  is  attracted  when  the  current  passes, 
and  is  pulled  away  from  the  magnet  by  a  spring,  when  the 
current  ceases  to  flow. 

If  a  coil  of  wire  is  revolved  in  a  place  where  there  is  magnetism, 
electricity  is  produced.  This  is  made  use  of  for  the  production 
of  electricity  in  large  quantities.  The  more  electricity  produced, 
the  harder  it  is  to  move  the  coil  of  wire.  A  machine  for  this 
purpose  is  called  a  dynamo,  and  resembles  an  electric  motor. 

The  telephone  is  a  very  useful  application  of  electricity,  and 
the  student  should  consult  the  references  for  a  fuller  consid- 
eration of  it,  as  well  as  for  details  concerning  all  of  the  appli- 
cations of  electricity. 

References :  — 

1.   1803 :  312-342.          The  Dynamo,  Motor,  and  Magnetic   In- 
duction. 

a.    1801 :  391-392.     The  Dynamo-Electric  Machine. 
6.    1804 :  595-606.     The  Telegraph  and  the  Telephone. 

c.  1805:401-404.     Electric  Bell  and  the  Telegraph. 

d.  1807  :  365-369.     Electric  Bell  and  Telegraph. 

e.  1808 :  353-363.     Electric  Bell,  Telegraph,  and  Telephone. 
/.    1809:436-445.     Electric  Bell,  Telegraph,  and  Telephone. 
g.    1810:288-300.     The  Telegraph  and  Electromagnetic  In- 
duction. 

h.   1811 :  280-291.     The  Electromagnet,  Telegraph,  and  Bell. 


90  INTRODUCTION  TO  GENERAL  SCIENCE 

Experiment  29.  —  The  Electric  Bell,  Telegraph,  and  Tele- 
phone. 

Apparatus :  Galvanometer  which  was  made  in  Experiment 
28,  large  nail,  smaller  nail,  fifty  feet  No.  20  insulated  copper 
wire,  dry  cell,  steel  magnet  and  coil  which  was  made  in  Ex- 
periment 28. 

a.  Wind  nearly  all  of  the  wire  upon  the  large  nail  in  smooth 
layers;   fasten  one  end  of  the  wire  to  the  small  nail,  taking 
care  that  the  bare  copper  comes  into  contact  with  it ;  fasten  the 
other  end  to  one  of  the  dry  cell  terminals,  and  connect  a  wire  to 
the  other  terminal  of  the  dry  cell.     When  this  wire  is  touched 
to  the  small  nail,  it  is  attracted  to  the  large  nail.    If  care  is  used, 
the  small  nail  may  be  made  to  vibrate  very  rapidly.     When  a 
single  tap  is  made  by  the  small  nail,  the  telegraph  is  illustrated; 
if  the  small  nail  vibrates,  we  have  a  simple  electric  buzzer, 
which  would  ring  a  bell  if  the  latter  were  properly  placed. 

b.  Attach  the  ends  of  the  coil,  in  which  the  steel  magnet 
lies,  to  the  galvanometer,  with  wires  which  are  at  least  six 
feet  long.     Bring  a  piece  of  iron  (the  nail)  up  to  the  magnet, 
and  note  the  deflection.     Pull  the  iron  away  and  note  the  de- 
flection.    The  motions  must  be  rapid.     What  do  you  con- 
clude?    This   illustrates  the   simple   telephone.     When   the 
voice  strikes  the  iron  plate  of  a  receiver  used  as  a  transmitter, 
it  is  made  to  vibrate,  and  currents  are  caused  to  flow  in  the 
wire  around  the  magnet  in  the  back  of  the  iron  plate.     These 
currents  affect  a  similar  plate  in  the  other  receiver,  and  it 
makes  the  same  movements  as  does  the  first  iron  plate. 

66.    CHEMICAL  EFFECTS  OF  ELECTRICITY 
Electricity,   when  passing  through   a   chemical   solution, 
tends  to  separate  the  chemicals  into  their  components.     Thus 
water  is  separated  into  two  volumes  of  hydrogen  and  one 


CHEMICAL   EFFECTS  OF  ELECTRICITY  91 

volume  of  oxygen.  A  solution  which  contains  copper  is  sep- 
arated into  copper  and  the  other  constituents,  thus  making 
copper  plating  possible.  Nearly  all  of  the  metals  may  be 
used  for  electroplating,  and  they  may  be  purified  by  this 
method.  The  electric  energy  may  be  utilized  to  produce 
certain  forms  of  chemicals,  and  then  the  chemicals  may  be 
used  later  to  produce  electricity.  This  fact  is  made  use  of  in 
the  storage  cell.  The  lead  cell  consists  of  two  lead  plates 
which  are  immersed  in  dilute  sulphuric  acid.  The  plate  at- 
tached to  the  +  terminal  becomes  coated  with  lead  peroxide, 
while  the  other  plate  becomes  freed  from  all  oxygen  and  is 
practically  pure  lead.  The  lead  plates  now  act  as  if  they 
were  different  elements  and  produce  electricity  similarly  to 
a  rod  of  zinc  and  a  rod  of  carbon  in  dilute  acid.  The  Edison 
cell  uses  nickel  and  iron  for  the  plates. 

References :  — 

1.  1601 : 123.  The  Electrical  Sources  of  Soil  Nitrogen. 

2.  1703  :  38-39.  The  Electrolysis  of  Water. 

3.  1703  :  329-330.  The  Explanation  of  Electrolysis. 

4.  1803  :  292-298.  Chemical  Effects  of  Electricity, 
a.    1701:366.  Electroplating. 

6."  1801  :  349-354.  Electrochemical  Effects. 

c.  1804  :  474-478.  Chemical  Effects  of  the  Electric  Current. 

d.  1804:593-595.  Electrotyping. 

e.  1807  :  407-411.  Chemical  Effects  of  Currents. 
/.  1809:400-401.  The  Storage  Cell. 

Experiment  30.  —  Electroplating. 

Apparatus :  Two  dry  cells  with  carbon  of  one  connected  with 
zinc  of  the  other,  or  one  storage  cell,  beaker  250  c.c.,  strips  of 
copper,  I"x5",  connecting  wires,  German  silver  wire  No.  22. 

Materials:  Copper  sulphate,  paraffin,  sandpaper,  nitric 
acid,  10  per  cent,  benzine. 


92  INTRODUCTION  TO  GENERAL  SCIENCE 

a.  Fill  the  beaker  with  a  saturated  solution  of  copper  sul- 
phate, attach  one  copper  strip  by  a  wire  to  the  positive  ter- 
minal of  the  source  of  electricity,  and  insert  it  in  the  solution. 
Sandpaper  the  other  copper  strip  and  dip  it  into  melted  paraf- 
fin. When  the  paraffin  becomes  set,  scratch  your  initials, 
or  make  some  design,  in  the  wax,  taking  care  to  cut  into  the 
copper.  Dip  the  strip  in  10  per  cent  nitric  acid,  and  then  put 
it  immediately  into  the  copper  sulphate  solution.  Connect 
it  with  the  negative  terminal  of  the  source  of  electricity,  using 
some  of  the  German  silver  wire.  The  latter  regulates  the 
flow  of  electricity  on  account  of  its  high  resistance.  If  bubbles 
collect  on  the  engraving,  too  much  current  is  passing,  and 
more  German  silver  should  be  added  to  the  circuit.  In  half 
an  hour  the  initials  should  be  raised  enough  to  be  visible. 
Melt  off  the  wax,  and  clean  with  benzine.  If  the  strip  of 
copper  is  heated,  it  will  become  oxidized,  and  then  if  the  en- 
graving or  raised  letters  are  sandpapered,  they  will  stand  out 
in  contrast. 

Experiment  31.  —  The  Storage  Cell. 

Apparatus :  Three  dry  cells,  electric  bell,  two  strips  of  lead 
I"x5",  beaker  250  c.c.,  wires. 

Materials:  Dilute  sulphuric  acid  10  per  cent. 

a.  Connect  the  three  dry  cells  in  series,  carbon  of  one  cell 
with  zinc  of  the  next  cell,  and  connect  the  free  ends  to  the 
two  lead  strips.  Place  the  strips  in  the  beaker  so  that  they 
do  not  touch,  and  fill  the  beaker  nearly  full  of  dilute  sulphuric 
acid.  Allow  the  current  to  pass  for  two  or  three  minutes. 
Note  the  bubbles.  They  are  hydrogen  and  oxygen.  Dis- 
connect wires  from  dry  cell,  and  connect  them  to  the  bell.  It 
should  ring  for  a  few  seconds.  Why  does  the  bell  stop  ring- 
ing ?  Charge  the  storage  cell  again,  but  in  the  opposite  direc- 


HEAT   AND  LIGHT  FROM  ELECTRICITY  93 

tion.  Again  use  the  stored  energy  to  ring  the  bell.  Repeat 
several  .times,  each  time  reversing  the  charging.  Does  the 
bell  ring  longer  ?  Examine  the  lead  plates  and  give  a  reason. 

67.    HEAT  AND  LIGHT  FROM  ELECTRICITY 

Whenever  electricity  passes  through  a  substance,  it  meets 
with  more  or  less  resistance,  according  to  the  material.  Wher- 
ever there  is  resistance,  heat  is  produced.  The  incandescent 
lamp  is  an  example  of  heat,  as  well  as  light,  being  produced  by 
electricity.  Very  often  fires  have  been  caused  by  overheated 
electric  wires.  In  nearly  every  circuit,  however,  there  is 
inserted  a  piece  of  wire  of  low  melting  point,  which  melts 
when  an  excessive  current  passes,  and  thus  protects  the  rest 
of  the  circuit. 

References :  — 

1.   1803:305-311.  Heat  and  Light  from  Electricity, 

a.    1801 :  400-403.  The  Electric  Light. 

6.    1804  :  587-593.  The  Electric  Light. 

c.  1805  :  456-462.  Heat  Effects  of  Electricity. 

d.  1807 : 385-388.  Heat,    Light,  and  Power    from    Electric 

Currents. 

e.  1808  :  305-306.     Heating  Effects  of  the  Electric  Current. 
/.    1808  :  363-365.     Electric  Lighting. 

g.   1809  :  445-451.     Heat  and  Light  from  Electricity. 

h.   1811 :  317-318.     The  Incandescent  Lamp  and  the  Arc  Light. 

Experiment  32.  —  Heat  and  Light  from  Electricity. 

Apparatus :  Two  or  three  dry  cells,  or  a  storage  cell,  German 
silver  wire  No.  30,  iron  wire  No.  30,  file. 

a.  Connect  the  cells  in  series  and  pass  the  current  through 
an  inch  of  the  fine  wire.  Note  the  rapidly  increasing  tem- 
perature and  the  light  which  is  produced.  Iron  melts  at 
about  2200°  Fahrenheit.  What  do  you  think  about  the  pro- 


94  INTRODUCTION  TO  GENERAL  SCIENCE 

duction  of  heat  by  electricity  ?  Red-hot  temperature  is  about 
950°  Fahrenheit. 

6.  Attach  one  wire  from  the  three  cells  to  a  file,  and  rub  tn<> 
other  wire  on  it.  What  do  you  see  ? 

c.  If  there  is  electric  power  in  the  building,  the  teacher  may 
show  these  effects  to  a  startling  degree. 

68.    HEAT  PRODUCES  LIGHT 

We  learned  in  Section  2  that  heat  is  due  to  the  motions  of 
the  molecules,  and  in  Section  3  that  if  the  molecular  motion 
becomes  rapid  enough,  the  substance  changes  from  a  solid  to  a 
liquid  and  then  to  a  gas.  These  changes  concern  the  material 
alone.  There  is  another  effect  which  is  produced  by  the 
rapidly  moving  molecules,  and  we  call  the  visible  result  light. 

All  space  between  all  bodies,  and  between  the  molecules  of 
every  substance,  is  filled  with  what  is  usually  called  ether,  and 
sometimes  light-bearing  ether,  to  distinguish  it  from  the  an- 
aesthetic. When  the  motions  of  the  molecules  are  rapid 
enough,  waves  similar  to  but  very  much  smaller  than  water 
waves  are  set  up  in  this  ether.  All  these  waves  of  the  ether 
are  electric  waves,  few  of  which  affect  the  eye,  but  all  of 
which  transmit  energy.  Since  one  form  of  energy  can  be 
changed  into  all  other  forms,  we  obtain  heat,  light,  and  chemi- 
cal effects  from  the  sun. 

If  a  piece  of  metal  is  gradually  heated,  it  begins  to  glow  at 
about  950°  Fahrenheit,  525°  Centigrade,  and  increases  in 
brightness  up  to  dazzling  white  at  about  2200°  Fahrenheit, 
1200°  Centigrade.  This  is  true  only  if  the  metal  does  not 
turn  into  a  gas.  A  very  good  example  is  the  tungsten  in- 
candescent lamp,  for  metals,  and  the  ordinary  incandescent 
lamp,  for  carbon. 


LIGHT  AND   VISION  95 

References :  — 

1.  1002:399-403.  The  Production  of  Light  —  the  Electron. 

2.  1304 :  234.  Heat  and  Light. 

3.  1601 : 12-13.  Heat  Produces  Light. 

4.  1710 :  46-47.  Heat  Produces  Light. 

5.  1803  :  463-464.  Radiation  and  Absorption. 

a.  1804  :  317.  Molecular  Motion  Produces  Light. 

b.  1805  :  215.  Heat  a  Source  of  Light. 

c.  1807  :  257-258.  Heat  Produces  Light. 

d.  1809  :  274.  Heat  Produces  Light. 

e.  1811 :  220-222.  Natural  and  Artificial  Sources  of  Light. 

Experiment  33.  —  Heat  Produces  Light. 

Review  the  heating  and  lighting  effect  of  the  electric  cur- 
rent. Regulate  the  amount  of  current  which  passes  through 
an  incandescent  lamp  by  means  of  a  long  piece  of  German 
silver  wire  of  small  diameter.  The  same  plan  may  be  used  in 
connection  with  a  small  piece  of  iron  wire  and  the  dry  cells. 

69.    LIGHT  AND  VISION 

While  existence  requires  heat  and  food  and  air,  vision,  as  we 
understand  it,  could  not  exist  without  light,  and  life  would  be 
very  empty.  We  must  consider  that  light  is  due  to  electric 
waves  sent  out  by  a  body,  which,  by  virtue  of  temperature, 
or  chemical  change,  can  produce  these  waye  motions.  When 
these  waves  strike  the  eye,  we  receive  the  sensation  of  light, 
and  while  the  waves  would  be  there,  just  the  same,  whether 
they  struck  the  eye  or  not,  they  would  not  produce  the  same 
result.  It  may  practically  be  said  that  if  there  is  not  an  eye 
to  see,  there  is  no  light.  Those  particular  waves  which  pro- 
duce the  sensation  of  light  in  the  eye  do  not  produce  other 
effects  to  any  extent,  for  the  heat  effect  and  the  chemical 
effects  which'  we  receive  are  due  to  waves  of  a  different 


96  INTRODUCTION  TO  GENERAL  SCIENCE 

length.     There  are  however,  some  heat  and  some  chemical 
effects  produced  by  all  of  the  waves. 

All  objects,  except  those  which  produce  light,  are  seen  on 
account  of  light  which  they  reflect.  (See  next  section.)  If 
there  is  no  light  to  be  reflected,  the  objects  must  become  in- 
visible. No  animal  can  see  in  complete  darkness,  although 
some  animals  can  see  in  very  dim  light.  Section  78  describes  a 
method  of  light  measurement.  Vision  is  treated  in  Section  199. 

References :  — 

1.  1002:398-399.  The  Nature  of  Light. 

2.  1304:232.  Light. 

3.  1803  :  404-405.  The  Nature  of  Light. 

4.  1803  :  409.  The  Sources  of  Light  Waves. 

a.  1801 :  188-190.  Light  —  Speed  of  Light. 

b.  1802 :  202-204.  Theories  of  Light. 

c.  1804 :  318-319.  Light  Defined. 

d.  1805:213-214.  Nature  of  Light. 

e.  1806  :  138-140.  Nature  of  Light. 

/.    1807 :  255-257.     Nature  and  Transmission  of  Light. 
g.   1808 :  373-374.     Nature  of  Light. 

70.    REFLECTION 

When  light  strikes  against  a  smooth,  bright  surface,  it  is 
bent  back  and  is  said  to  be  reflected.  In  this  case  there  is  very 
little  absorption,  and  nearly  all  the  energy  is  returned.  The 
angle  at  which  the  light  leaves  such  a  reflecting  surface  is 
equal  to  the  angle  at  which  the  light  strikes  it.  We  say  that 
the  angle  of  reflection  is  equal  to  the  angle  of  incidence.  Light- 
colored  materials  reflect  more  light  than  the  darker  shades, 
and  smooth  surfaces,  especially  polished  metallic  surfaces, 
reflect  the  most.  The  absorption  in  an  ordinary  mirror  is 
about  10  per  cent. 


REFLECTION  97 

References :  — 

1.  1103 : 168-169.  Reflection  of  Light. 

2.  1304 :  235-236.  Reflection  and  Absorption. 

3.  1803:395-396.  Reflection, 
a.   1305  :  102-103.  The  Mirage. 
6.    1801 : 196-197.  Reflection. 

c.  1802  :  212-217.  Reflection  of  Light. 

d.  1804  :  331.  Reflection  of  Light. 

e.  1805:225-227.  Reflection. 
/.  1806  :  150-151.  Reflection. 

g.    1807  :  268-269.     Reflection  of  Light. 

h.    1808:382-383.     Reflection. 

i.    1809  :  283-288.    Reflection  at  Plane  Surfaces. 

Experiment  34.  —  Reflection. 

Apparatus :  Piece  of  mirror  glass  5"  X  2"  with  a  transverse 
scratch  at  its  middle  point,  block  of  wood  5"  X  2",  two  elas- 
tic bands,  pins,  protractor. 

Materials :  Sheet  of  note  paper. 

a.  Draw  a  straight  line  across  the  paper  and  place  the  mir- 
ror, attached  to  the  block  of  wood  by  means  of  the  elastic 
bands,  so  that  the  silvered  surface  lies  along  the  line.  Slip  the 
protractor  under  the  edge  of  the  mirror  so  that  its  diameter  is 
also  on  the  line,  with  its  middle  point  under  the  scratch. 
Mark  every  5°  on  the  paper,  at  the  edge  of  the  protractor, 
numbering  from  zero,  at  the  middle  mark,  to  ninety  at  each 
end  of  the  diameter. 

6.  Stick  a  pin  at  the  5°  mark  and  look  for  its  reflection  in  the 
mirror.  Stick  another  pin,  near  the  protractor,  in  line  with 
the  reflection  and  the  center  mark.  Where  is  the  last  pin  ? 

c.  Make  several  trials,  sticking  the  first  pin  in  different 
places.  Are  you  satisfied  with  your  results?  Tabulate 
them. 


98  INTRODUCTION  TO  GENERAL  SCIENCE 


71.    COLOR 

It  is  customary  to  speak  of  the  color  of  objects,  as  if  color 
existed.  There  is  really  no  such  a  thing  as  color,  except  as  a 
sensation.  Colors  are  not  due  to  materials,  as  such,  but  to 
the  fact  that  some  materials  are  capable  of  absorbing  part  of 
the  light  and  reflecting  the  rest.  White  light  is  made  up  of 
all  the  colors  of  the  rainbow.  (See  next  section.)  Accord- 
ingly, if  we  look  at  some  material  which  absorbs  all  colors 
except  red,  it  will  appear  red.  This  is  because  it  reflects  the 
red  light,  or,  more  scientifically,  it  reflects  those  particular 
wave  lengths  which  give  to  our  eye  the  sensation  of  red.  The 
same  explanation  applies  to  all  other  colors.  If,  on  the  other 
hand,  we  use  some  source  of  light  which  does  not  produce 
pure  white  light,  objects  do  not  appear  the  same  by  it  as  by 
sunlight.  This  is  because  some  of  the  waves  which  the  object 
can  reflect  are  not  present,  and  therefore  cannot  be  reflected. 

The  color  of  the  sky  is  due  to  the  fact  that  the  light  is  par- 
tially blocked  by  small  particles  of  dust  in  the  air;  those  par- 
ticular wave  lengths  which  gives  us  the  sensation  of  blue  are 
blocked  most,  and  are  thus  either  stopped  or  reflected.  Ex- 
cept in  the  neighborhood  of  the  sun,  the  light  which  illumi- 
nates the  sky  is  due  to  light  which  has  struck  the  earth  and  has 
been  reflected  up  to  the  sky.  Most  of  the  light  which  has 
been  reflected  from  the  earth  passes  on  into  space,  but  those 
very  short  wave  lengths  which  give  us  the  sensation  of  blue 
are  reflected  back  by  the  particles  of  the  air,  and  we  see  the 
sky  as  blue.  The  fact  is,  the  sky  is  absolutely  black;  that  is, 
it  has  no  color  whatsoever.  In  those  countries  where  there 
are  no  manufactories,  and  where  the  air  is  extraordinarily  clear, 
the  sky  is  very  dark  blue;  and  balloonists  tell  us  that  the 


COLOR  99 

farther  they  ascend  into  the  air,  the  darker  the  sky  becomes. 
If  the  air  were  absolutely  pure,  we  would  have  a  black  sky. 

References :  — 

1.  1103  : 170-171.  Colors  of  the  Sky. 

2.  1304 :  233.  The  Cause  of  Colors. 

3.  1601:7.  Color. 

4.  1803  :  443-450.  Color  Phenomena. 

a.  1305  :  103-105.  Color  of  the  Atmosphere. 

6.  1801:238-241.  Color. 

c.  1802 :  258-260.  Color  —  Color  Sensation. 

d.  1804:386-391.  Color. 

e.  1805:244-247.  Color. 

/.    1807 :  322-332.     Dispersion  and  Color. 

g.   1808:418-421.     Color. 

h.    1811:214-220.     Cause  of  Color. 

Experiment  35.  —  Color. 

Apparatus :  Alcohol  or  gas  lamp,  asbestos  paper  to  fit  lamp 
as  a  collar,  pieces  of  cloth  colored  red,  yellow,  and  blue,  beaker 
250  c.c. 

Materials :  Common  salt,  soap,  -solution  of  rosin  in  alcohol, 
(one  part  rosin,  ten  parts  alcohol). 

a.  Dip  asbestos  paper  in  saturated  solution  of  salt,  and 
fasten  around  burner.     Then  light  burner  and  darken  room. 
Hold  the  piece  of  cloth  near  the  flame.     What  color  is  the  red 
now?    The  yellow?    The  blue?     Conclusions?    Notice  the 
color  of  the  faces  of  your  companions.     Are  the  faces  rosy  ? 
Does  color  belong  to  an  object  itself? 

b.  Fill  beaker  with  water,  and  add  a  drop  or  two  of  the  rosin 
solution.     The  rosin  is  insoluble  in  water  and  is  suspended  in 
very  fine  particles.     What  color  is  the  water  by  reflected 
light  ?     By  light  which  has  passed  through  the  water,  that  is, 
transmitted  light  ?   Add  more  rosin  and  state  results.  What  is 
the  connection  between  this  experiment  and  the  color  of  the  sky  ? 


100         INTRODUCTION  TO  GENERAL  SCIENCE 


72.    REFRACTION  AND  DISPERSION 

If  a  beam  of  white  light  is  allowed  to  pass  through  a  tri- 
angular piece  of  glass,  or  other  transparent  medium,  it  is  not 
only  bent  towards  the  thicker  side  of  the  prism,  as  a  piece  of 
glass  so  shaped  is  called,  but  it  is  also  separated  into  the  seven 
primary  colors, — red,  orange,  yellow,  green,  blue,  violet,  and 
indigo.  These  colors  are  called  the  prismatic  colors,  since  they 
are  produced  by  means  of  a  prism.  The  bending  of  the  path 
of  light  is  called  refraction ;  the  separation  into  the  component 
color  is  called  dispersion. 

The  gorgeous  colors  of  sunrise  and  sunset  are  caused  by 
drops  of  water  in  the  atmosphere  breaking  up  the  white  light 
of  the  sun  into  the  primary  colors.  Some  of  these  colors  are 
scattered  or  bent  so  that  they  do  not  reach  the  eye.  We  then 
receive  the  sensation  which  is  due  to  the  other  colors.  In  a 
cloudless  sky,  with  a  very  small  amount  of  fog  or  haze,  there 
will  be  no  colors  in  the  sunset  or  the  sunrise. 

References :  — 

1.  1002 : 142-143.  Refraction  of  Light  by  the  Atmosphere. 

2.  1103  :  166-168.  Refraction  of  Light. 

3.  1103  : 169.  Diffraction  of  Light. 

4.  1304:232-233.  Color  Effects. 

5.  1803:398-399.  Refraction. 

a.  1801:211-142.  Refraction. 

b.  1801:230-231.  Dispersion. 

c.  1802  :  226-228.  Refraction. 

d.  1802:252.  Dispersion. 

e.  1804:346-348.  Refraction. 
/.  1804:368-370.  Dispersion. 
g.  1805:227-232.  Refraction. 
h.  1805:238-239.  Dispersion. 
i.  1806 : 171-175.  Refraction. 


THE  RAINBOW  101 

Experiment  36.  —  Refraction  and  Dispersion. 
Apparatus:    Triangular   glass    prism   60°,   one-inch  face, 
three  inches  long. 

a.  Place  prism  on  its  end,  on  piece  of  note  paper,  and  draw 
pencil  line  around  it.     Now  draw  a  straight  line,  three  inches 
long,  up  to  one  face  of  the  prism  at  an  angle  of  about  45°. 
Looking  through  that  side  of  the  prism  through  which  the  line 
would  come  out,  if  continued,  lay  a  rule  in  line  with  the  pencil 
line  as  seen  through  the  prism.     Draw  a  line  along  the  rule, 
remove  the  prism  and  connect  the  ends  of  the  two  long  lines 
by  means  of  a  short  one  across  the  outline  of  the  prism.    The 
complete  broken  line  indicates  the  path  of  light  through  the 
prism.     Which  way  is  it  bent  ? 

b.  Go  near  a  window,  and  pull  down  the  curtain  so  that 
only  a  narrow  beam  of  sunlight  enters  the  room.     Hold  the 
prism  in  this  beam  until  you  see  the  prismatic  colors.     Which 
color  is  bent  the  most  ?    How  many  colors  can  you  distinguish  ? 
Name  them. 

73.    THE  RAINBOW 

The  rainbow  is  well  named,  as  it  is  composed  of  raindrops 
which  occupy  positions  in  the  arc  of  a  circle.  A  rainbow  has 
no  existence ;  that  is,  it  is  a  condition,  tand  raindrops  which 
are  in  the  proper  position  at  one  instant  pass  out  of  that 
position  the  next  instant,  to  have  their  places  occupied  by 
other  raindrops. 

Each  drop  of  water  which  takes  part  in  the  production  of  a 
rainbow  acts  similarly  to  the  prism  in  Experiment  36.  All 
combined,  they  give  the  impression  of  bands  of  colors.  Every 
drop  of  water  which  sends  a  certain  kind  of  waves  to  the  eye 
is  at  an  equal  distance  from  the  eye.  Now  all  points  which 


102          INTRODUCTION  TO  GENERAL  SCIENCE 

are  equidistant  from  a  given  point  lie  on  the  arc  of  a  circle. 
That  is  why  a  rainbow  is  curved. 

References :  — 

1.  1103:174-175.          The  Rainbow. 

2.  1803  :  452-454.  The  Rainbow. 

a.  1801 :  232-235.  The  Rainbow  and  its  Cause. 

b.  1802 :  254.  The  Rainbow. 

c.  1804 :  370-371.  The  Rainbow. 

d.  1805 :  241-244.  The  Rainbow  and  its  Cause. 

e.  1807  :  335-337.  The  Rainbow. 
/.    1808 :  415-418.  The  Rainbow. 

g.   1809 :  324-325.     Action  of  a  Raindrop  on  Sunlight,  —  the 
Rainbow. 

Experiment  37.  —  The  Rainbow. 

Apparatus :  Piece  of  glass  3"  X  3",  medicine  dropper. 

Materials :   Lubricating  oil. 

a.  Rub  a  very  little  lubricating  oil  on  one  surface  of  the 
glass  plate  and  place  a  drop  of  water  on  it,  using  the  medicine 
dropper.  The  drop  must  be  small  enough  to  be  nearly  spheri- 
cal. Place  the  plate  in  the  sun  and  move  the  head  until,  in 
one  position  or  another,  all  the  colors  of  the  rainbow  have 
been  seen.  Why  is  the  oil  used  ?  Why  should  a  small  drop 
be  used  ? 

74.   DIFFUSION  OF  LIGHT 

A  mirror  reflects  light  in  a  regular  way.  This  is  true  of 
any  smooth  and  bright  surface.  Rough  bodies  reflect  light 
in  an  irregular  manner,  and  we  see  no  reflection  as  such, 
but  we  see  the  object  which  reflects  the  light.  This  is  called 
diffused  reflection. 

Light  is  diffused  to  a  very  great  extent  by  particles  of  dust 
in  the  air  which  are  too  small  to  be  seen.  We  obtain  the  light 


TWILIGHT  103 

from  the  sky  in  this  manner  of  diffused  reflection.  Since  the 
reflecting  surface  is  so  large,  there  are  no  definite  shadows  pro- 
duced, the  light  fading  away  gradually  on  all  sides  of  an  object. 
The  best  light  for  the  eyes  is  diffused  light.  Experiment  35 
showed  diffusion  of  light  by  means  of  the  suspended  particles 
in  the  water. 
References :  — 

1.  1304:233.  Diffraction  of  Light. 

2.  1803  :  396-397.  Diffusion  of  Light. 

a.  1801 :  197-198.  Diffused  Reflection. 

b.  1802  :  214.  Irregular  Reflection  —  Diffusion. 

c.  1804  :  333-335.  Diffused  Light. 

d.  1805  :  225.  Diffusion  of  Light. 

e.  1807  :  269-270.  Diffusion  of  Light. 
/.  1809  :  284r-285.  Diffused  Light. 

g.    1810 :  337-338.     Regular  and  Irregular  Reflection. 
h.   1811 :  222.  Diffused  Reflection  of  Light. 

75.    TWILIGHT 

After  the  sun  sets,  darkness  does  not  begin  immediately. 
In  fact,  the  western  sky  becomes  brighter  a  little  while  after 
the  sun  has  set  than  it  was  just  at  sunset.  This  is  called  the 
afterglow,  and  is  due  to  the  reflection  of  light  from  particles 
in  the  higher  air.  In  a  very  dry,  clear  atmosphere  the  after- 
glow is  not  so  marked  as  it  is  in  a  locality  where  there 'is  more 
water  and  dust  held  in  suspension  in  the  atmosphere.  This 
dust  is  not  to  be  confused  with  the  dust  of  the  earth  as  we  find 
it  in  streets,  for  it  is  very  fine  and  practically  invisible. 

Twilight  means  two  lights,  —  the  sun  and  the  stars,  —  and 
lasts  usually  until  the  sun  is  18°  below  the  horizon. 
References :  — • 

1.  1002 :  138.  Twilight  Due  to  the  Atmosphere. 

2.  1103:24-25.  Length  of  Twilight. 


104         INTRODUCTION  TO  GENERAL  SCIENCE 

a.    1305:101-102.     Twilight. 

6.   1804 :  356.  Cause  of  Twilight. 

76.    TRANSMISSION  OF  LIGHT  —  SHADOWS 

Objects  which  allow  light  to  pass  through  them  undimmed 
are  called  transparent.  If  the  light  is  much  diminished,  so 
that  only  a  little  shines  through  dimly,  the  object  is  called 
translucent.  If  no  light  can  pass  through  a  body,  it  is  called 
opaque.  When  no  light  passes  through  an  object,  it  casts  a 
shadow  which  has  the  same  outline  as  the  object.  Therefore 
we  conclude  that  light  travels  in  straight  lines.  The  brighter 
the  light,  the  denser  is  the  shadow. 

References :  — 

1.  1304:238-239.          Transmission  of  Light  through  the  At- 

mosphere. 

2.  1601 :  8.  Transmission  of  Light. 

3.  1803:391.  Shadows. 

4.  1803 :  409-410.          Why  Light  Travels  in  Straight  Lines. 

a.  1801:190-192.  Shadows. 

b.  1802:262.  Shadows. 

c.  1804:323-324.  Shadows. 

d.  1805  :  215-216.  Transmission  of  Light. 

e.  1805:220-221.  Shadows. 
/.  1806:142-143.  Shadows. 
g.  1807:260-261.  Shadows. 
h.  1808:374-375.  Shadows. 

i.   1809 :  276-278.     Shadows  —  Pinhole  Camera. 

77.    ECLIPSES 

All  planets,  including  the  moon  and  the  satellites  of  the 
other  planets  besides  the  earth,  shine  by  light  reflected  from 
the  sun.  Most  of  the  stars  shine  by  their  own  light;  that  is, 
they  are  all  bodies  like  our  sun,  although  at  a  very  great  dis- 


MEASUREMENT  OF  LIGHT  105 

tance  from  it.  If  the  light  is  shut  off  from  the  moon,  or  from 
any  of  the  planets,  those  planets  cannot  be  seen.  We  know 
that  sometimes  the  earth  passes  between  the  sun  and  moon, 
and  casts  its  shadow  on  the  moon,  rendering  part  of  the  latter 
invisible.  We  call  this  shadow  over  another  heavenly  body 
an  eclipse.  In  the  same  way  we  can  have  eclipses  of  planets, 
but  because  they  are  so  small,  they  are  not  noticed  except 
through  a  telescope.  There  is  one  other  kind  of  eclipse,  which 
is  the  solar  eclipse.  This  is  caused  by  the  moon  passing  be- 
tween the  earth  and  the  sun.  In  that  condition  the  shadow 
is  upon  us,  and,  if  there  were  people  on  the  moon,  they  would 
see  that  the  earth  was  partially  eclipsed. 
References :  — 

1.  1002 :  273-275.          Conditions  for  Eclipses. 

2.  1002 :  284-287.          Uses  of  Lunar  and  Solar  Eclipses. 

3.  1304  :  2.  Shape  of  Earth  Shown  by  Lunar  Eclipse. 

4.  1803  :  391.  Shadow   and  Eclipses. 

a.    1001 :  161-174.  Eclipses  —  Kind  and  Number. 

6.    1003  :  123-132.  Eclipses  of  the  Moon  and  Sun. 

c.  1004  :  171-181.  Eclipses  of  the  Sun  and  Moon. 

d.  1309 : 18-19.  Eclipse  of  the  Moon. 

e.  1312  :  7-8.  Eclipses. 

/.    1808 :  375.  Umbra  and  Penumbra. 

g.    1809:276.  Shadows. 

78.   MEASUREMENT  OF  LIGHT 

Light  can  be  measured  by  the  direct  illumination  which  it 
can  produce,  or  by  the  shadows  which  it  casts.  The  inten- 
sity of  illumination  is  estimated  in  candle  power,  and  the 
standard  unit  of  measurement  is  a  sperm  candle,  .three- 
fourths  of  an  inch  in  diameter,  which  burns  at  the  rate  of  120 
grains  per  hour. 

Before  measuring  light  it  is  necessary  to  learn  that  the  in- 


106          INTRODUCTION  TO  GENERAL  SCIENCE 

tensity  of  illumination  does  not  fall  off  proportionally  to  the 
distance,  but  to  the  distance  squared.  Thus  a  light  at  three 
feet  gives  but  one-ninth  the  intensity  of  the  same  light  at  a 
distance  of  one  foot. 

If  a  standard  candle  and  another  source  of  light  give  the 
same  illumination  to  two  blocks  of  paraffin,  separated  by  tin- 
foil, and  placed  between  the  two  sources  of  light,  both  blocks 
appear  the  same  shade.  The  distances  of  the  two  lights  from 
the  block  may  be  measured,  and  the  intensity  of  the  unknown 
light  may  be  computed. 

Two  shadows  of  a  rod  may  be  obtained  side  by  side,  one 
from  a  standard  candle,  and  the  other  from  the  source  of  light 
which  is  to  be  measured.  The  distance  of  the  unknown 
may  be  varied  until  the  two  shadows  have  the  same  density. 
Then  the  distances  may  be  measured  and  the  unknown  candle 
power  computed.  Instruments  such  as  those  described  are 
called  photometers. 

References :  — 

1.    1803 :  392-395.  Intensity  of  Light  — Candle  Power. 

a.   1801 :  193-195.  Photometry. 

6.    1802  :  208-211.  Measurement  of  Light  —  the  Photometer. 

c.  1804 :  327-329.  Intensity  of  Illumination  —  Photometry. 

d.  1805  :  221-224.  Intensity  of  Light  —  Photometry. 

e.  1806:144-146.  Measurement  of  Light  —  Photometry. 

/.    1807:263-265.     Intensity  of  Illumination  —  The  Photom- 
eter. 

g.  1808  :  377-379.  Intensity  of  Illumination  —  Photometry. 
h.  1809  :  279-281.  Illumination,  Photometry,  Photometers. 
i.  1810 :  333-337.  Photometry,  Photometers,  Candle  Power. 

Experiment  38.  —  Candle  Power  —  The  Photometer. 
Apparatus:    A   block   of  wood   3"X3"X1"   with   a  peg 
6"  X  1"  inserted  in  one  side,  two  blocks  3"X2"X  I",  meter 


PHOTOGRAPHY  107 

stick,  simple  screen  (cardboard  3"  X  3"  standing  in  slotted 
block). 

Materials:  One  candle  mounted  on  a  block,  four  candles 
mounted  on  a  block. 

a.  Place  peg  as  near  to  screen  as  possible  and  place  the  one 
candle  20  cm.  from  the  peg.  How  far  away  do  you  have  to 
place  the  four  candles  to  obtain  a  shadow  as  dense  as  the  one 
candle  casts  ?  Repeat,  placing  single  candle  at  a  distance  of 
30  cm.  A  slightly  darkened  room  is  desirable. 

6.  Using  this  method  test  the  candle  power  of  an  incan- 
descent lamp  at  home.  Also  test  the  candle  power  of  a  gas 
flame  and  of  a  kerosene  lamp  by  this  means.  Make  your 
own  photometer. 

79.  PHOTOGRAPHY 

The  waves  near  the  violet  end  of  the  spectrum  are  the  most 
active  in  the  production  of  chemical  changes,  and  they  are  also 
those  which  kill  the  bacteria  of  disease.  Proper  ventilation 
and  sunlight  can  do  much  toward  sanitation. 

The  chemical  effect  which  is  made  use  of  to  the  greatest 
extent  in  the  arts  is  that  of  sunlight  upon  the  combinations  of 
silver  and  other  elements.  Silver  chloride  and  silver  bromide 
turn  dark  in  the  sunlight,  due  to  the  separation  of  metallic 
silver  from  its  compound.  After  a  silver-salt  has  been  exposed 
to  light,  it  can  be  assisted  in  the  separation  of  metallic  silver 
by  certain  chemicals,  called  developers.  They  are  known 
chemically  as  reducing  agents. 

There  are  other  photographic  effects  of  light  which  are  not 
commonly  thought  of  under  this  title.  The  tanning  of  the 
skin  is  just  as  truly  a  chemical  change,  and  a  photographic 
result,  as  is  the  breaking  down  of  a  silver  compound. 

The  details  of  photography,  although  very  interesting,  and 


108          INTRODUCTION  TO  GENERAL  SCIENCE 

worthy  of  study,  must  be  obtained  from  special  books.  The 
references  give  the  chemistry  of  photography  and  some  of  its 
uses. 

References :  — 

1.  1703:373-375.          Photography. 

2.  1803:433-434.  The  Camera. 

a.  1003  :  233-236.  Uses  of  Photography  in  Astronomy. 

6.  1701 :  367-368.  Photography. 

c.  1704:354-356.  Photography. 

d.  1705:220-221.  Photography. 

e.  1706:312-313.  Photography. 
/.  1707:391-392.  Photography. 
g.  1708 ;  375-376.  Photography, 
i.  1709:308-311.  Photography. 
i.  1711:155-158.  Photography. 

j.    1713  : 156-158.     Photochemistry. 

Experiment  39.  —  Effect  of  Light  upon  a  Silver  Salt. 

Apparatus :  Test  tubes  6"  X  f",  funnel,  ring  stand. 

Materials:  Silver  nitrate  solution,  10  per  cent,  hydro- 
chloric acid,  25  per  cent,  potassium  bromide  solution,  10  per 
cent,  potassium  iodide  solution,  10  per  cent,  several  sheets 
of  filter  paper. 

a.  Take  5  c.c.  of  silver  nitrate  solution  in  a  test  tube  and 
add  hydrochloric  acid,  drop  by  drop,  until  there  is  no  further 
precipitate  formed.  You  have  seen  a  chemical  change. 
Silver  nitrate  has  been  changed  into  silver  chloride.  Filter, 
using  the  funnel,  and  expose  the  residue  to  direct  sunlight. 
What  happens?  Repeat,  using  potassium  bromide  and 
potassium  iodide  solutions.  Which  material  changes  the 
fastest  in  the  sunlight? 


THE  ATMOSPHERE  AND  ITS  COMPOSITION     109 


80.  THE  ATMOSPHERE  AND  ITS  COMPOSITION 

It  is  necessary  for  every  living  being  to  breathe,  and  the 
oxygen  required  is  supplied  from  the  atmosphere  which  sur- 
rounds the  earth.  This  atmosphere  obtains  its  name  from 
two  Greek  words  meaning  "  breath-sphere."  It  extends  up 
from  the  earth  between  two  and  three  hundred  miles,  but, 
since  it  is  very  compressible,  fully  half  of  all  the  atmosphere 
is  within  three  miles  of  the  surface  of  the  earth. 

The  composition  of  the  atmosphere  is  not  uniform.  This 
fact  proves  that  the  atmosphere  is  not  a  chemical  compound, 
but  merely  a  mixture  of  various  gases.  It  can  therefore  be 
separated  mechanically  into  its  component  parts,  which  con- 
sist roughly,  by  volume,  of  nitrogen,  78  per  cent,  oxygen,  21 
per  cent,  and  argon,  1  per  cent.  Besides  these,  very  small 
quantities  of  carbon  dioxide,  ozone,  dust,  bacteria,  and  other 
rarer  substances  are  present.  The  amount  of  carbon  dioxide, 
bacteria,  and  dust  depends  upon  the  locality.  These  are 
called  impurities,  and  pure  air  necessarily  contains  a  very 
small  amount  of  them. 

References :  — 

1.  1002 : 135-143.  The  Earth's  Atmosphere  and  its  Effects. 

2.  1304:229-231.  Composition  and .  Weight  of  the  Atmos- 

phere. 

3.  1702  :  66-71.  Air  —  a  Mechanical  Mixture. 

4.  1803  :  68-70.  Extent  and  Character  of  Earth's  Atmos- 

phere. 

a.  1102  :  2-8.  Origin,  Evolution,  and  Future  of  the  At- 

mosphere —  Its  Composition. 

6.  1301 :  33-41.  Composition  and  Height  of  the  Atmos- 
phere. 

c.  1302  :  273-275.      Composition  of  the  Atmosphere. 

d.  1303  :  23-26.          The  Atmosphere. 


110          INTRODUCTION  TO  GENERAL  SCIENCE 

e.    1305  :  55-58.  Composition  and  Uses  of  Atmosphere. 

/.    1307  :  214-216.  The  Atmosphere  and  its  Properties. 

g.   1701 :  83-91.  The  Atmosphere  and  its  Properties. 

h.  1707  :  140-146.  The  Air  and  its  Constituents. 

i.    1709  : 170-176.  Composition  of  the  Atmosphere. 

Experiment  40.  —  Composition  of  Air. 

Apparatus:  Beaker  150  c.c.,  crystallization  dish  4"  in 
diameter,  flat  cork  1"  in  diameter. 

Materials :  Piece  of  yellow  phosphorus  size  of  a  pea. 

a.  Fill  crystallization  dish  half  full  of  water,  float  the  piece 
of  phosphorus  on  the  cork,  and  invert  the  beaker  over  it.  If 
beaker  does  not  stay  in  place,  put  a  small  weight  upon  it. 
Leave  for  twenty-four  hours.  How  high  does  the  water  rise  ? 
Phosphorus  combines  with  the  oxygen  of  the  air  and  leaves 
the  nitrogen  and  other  constituents  of  the  atmosphere. 

81.    WEIGHT  OF  THE  AIR 

We  learned  in  Section  2  that  all  matter  is  composed  of 
molecules,  and  in  Section  3  that  the  difference  between  solids, 
liquids,  and  gases  is  chiefly  that  of  the  relative  velocity  of  the 
molecules.  We  would  expect,  therefore,  that  matter,  in  any 
of  its  states,  would  have  weight  on  account  of  gravitation. 
See  Section  39,  Universal  Gravitation. 

The  total  weight  of  the  air,  or  atmosphere,  is  not  of  special 
interest.  The  number  of  tons  means  nothing  to  us,  for  we 
cannot  comprehend  its  vastness.  What  does  interest  us  is  the 
weight  of  the  atmosphere  on  each  square  inch  of  surface, 
wherever  we  may  be.  The  weight  per  unit  area  is  called 
pressure.  At  the  surface  of  the  ocean  the  pressure  of  the  at- 
mosphere is  14.7  pounds  per  square  inch,  or,  approximately,  a 
long  ton  per  square  foot.  Sea  level  is  taken  as  the  real  level 
of  the  earth's  surface. 


WEIGHT  OF   THE  AIR  111 

The  winds,  which  are  to  be  studied  in  Section  94,  show  con- 
clusively that  air  has  weight.  Otherwise,  winds  could  not 
exist,  or,  if  air  did  move,  its  effect  would  be  invisible  and  unfelt. 


1.    1304:231-232. 
2.    1803:58. 

Effect  of  Gravity  on  Air. 
The  Weight  of  Air. 

3.   Farmer's  Bulletin  No.  408  :  21-23.    To  Make  a 

Balance. 

a.   1102:143. 

The  Weight  of  the  Air. 

6.    1305:56. 

Weight  of  Air. 

c.    1309:202-203. 

Weight  of  the  Air. 

d.  1310:323. 

Substantiality  of  the  Air. 

e.    1311:225-226. 

Weight  and  Height  of  the 

Atmosphere. 

/.    1801:122. 

Air  has  Weight. 

g.    1804:155-156. 

Atmospheric  Pressure. 

h.   1805:129-130. 

Weight  of  the  Air. 

i.    1806:51-52. 

Weight  of  Air. 

j.    1807:31-32. 

Weight  and  Pressure  of  the  Atmosphere. 

k.   1808:143. 

Weight  of  Gases. 

Experiment  41.  —  Weight  of  Air. 

Apparatus  :  Flask  250  c.c.,  rubber  stopper  to  fit,  ring  stand, 
asbestos  mat,  burner,  balances  and  weights.  (Home-made 
balances  will  do.) 

a.  Put  about  50  c.c.  of  water  into  the  flask  and  let  it  boil 
vigorously.  This  drives  out  the  air.  While  the  water  is 
boiling,  insert  the  stopper  and  remove  from  the  heat  immedi- 
ately. A  cloth  wet  with  cold  water  and  -wrapped  around  the 
flask  will  prevent  all  danger  of  an  explosion.  Weigh  the  flask. 
Then  remove  the  stopper,  thus  admitting  the  air,  and  weigh 
again.  Conclusions  ? 

The  home-made  balances  may  be  constructed  from  a  stick 
three  feet  long  with  a  cross  section  of  1"  X  \"  .  Insert  an  iron 
screw  eye  in  the  edge  of  the  stick  at'  the  middle,  and  suspend 
the  stick  by  a  string  through  the  screw  eye.  A  piece  of  iron, 
lead,  or  stone  may  be  attached  by  loop  of  string,  on  one  side  of 


112          INTRODUCTION  TO  GENERAL  SCIENCE 

the  balance,  and  the  flask  may  be  suspended  from  the  other 
side  in  a  similar  manner.  Equilibrium  may  be  easily  ob- 
tained, which,  when  destroyed,  shows  a  loss  or  gain  of  weight. 
The  actual  amount  of  loss  or  gain  is  of  no  consequence. 

82.    ATMOSPHERIC  PRESSURE  AND  THE  BAROMETER 

The  pressure  of  the  atmosphere  may  be  measured  by  an 
instrument  called  the  barometer.  It  consists  of  a  tube  more 
than  30  inches  long,  closed  at  one  end,  filled  with  mercury, 
and  inverted  in  an  open  dish  of  mercury.  Within  the  tube 
the  mercury  falls  until  its  surface  is  about  30  inches,  or  76 
centimeters  above  the  open  surface.  Above  the  mercury  in 
the  tube  is  a  vacuum.  If  the  amount  of  mercury  in  the  tube 
is  weighed,  and  its  weight  is  divided  by  the  cross  section  of 
the  tube,  the  result  will  approximate  14.7  pounds  per  square 
inch.  Since  water  is  only  about  one-fourteenth  as  heavy  as 
mercury,  a  water  barometer  would  have  to  be  about  four- 
teen times  as  long  as  a  mercury  barometer.  That  is,  to  be 
exact,  the  column  of  a  water  barometer  would  be  34  feet  long. 

At  sea  level  the  pressure  averages  14.7  pounds  per  square 
inch,  but  at  any  other  elevation  it  varies,  being  less  on  moun- 
tains, and  greater  in  places  below  sea  level.  If  we  ascend 
and  leave  some  of  the  atmosphere  below  us,  it  would  seem  nat- 
ural for  that  part  still  remaining  above  us  to  have  less  pres- 
sure than  the  whole.  Elevations  may  be  roughly  deter- 
mined by  means  of  the  barometer.  A  difference  of  reading  of 
one  millimeter  indicates  a  rise  of  about  twelve  meters.  This 
corresponds  to  one-tenth  of  an  inch  for  each  90  feet  of 
elevation. 

References :  — 

1.  1103  :  73-75.  Air  Pressure. 

2.  1103:75-77.  The  Barometer. 

3.  1304 : 421-422.  The  Barometer. 


ATMOSPHERIC  PRESSURE  AND  THE  BAROMETER    113 

4.    1803  :  59-63.  The  Barometer. 

a.  1102:82-83.  The  Barometer. 

6.  1302  :  275-276.  The  Barometer. 

c.  1303  :  24-27.  Pressure  of  the  Atmosphere. 

d.  1309  :  203-204.  The  Barometer. 

e.  1310 :  374-375.  The  Barometer  and  Altitude. 
/.  1801 :  122-126.  The  Barometer. 

g.    1802  :  120-124.  The  Barometer. 

h.   1804 :  157-163.  How  Atmospheric  Pressure  is  Measured. 

i.    1805  :  139-143.  The  Barometer. 

j.    1807 :  33-36.  Measurement  of  Atmospheric  Pressure. 

k.    1808 :  145-148.  Measurement  of  Atmospheric  Pressure. 

Experiment  42.  —  Atmospheric  Pressure. 

Apparatus:  Glass  tumbler,  card  to  cover  it,  glass  tube  \" 
diameter,  40"  long  and  closed  at  one  end,  small  funnel,  evap- 
orating dish,  ring  stand,  meter  stick,  iron  pan,  piece  of  cloth. 

Materials:  Mercury. 

a.  Fill  the  tumbler  full  of  water,  place  the  card  over  it,  and, 
gently  pressing  on  the  card,  invert  the  glass  and  card.     Then 
remove  the  hand  from  the  card,  which  will  stay  in  place. 
What  holds  it  there  ?     By  placing  the  inverted  glass  on  a 
smooth  table,  the  card  may  be  removed,  leaving  the  glass  full 
of  water,  but  inverted.     How  can  such  a  glass  of  water  be 
removed  from  the  table  without  spilling  any  of  the  water? 

b.  Place  the  closed  end  of  the  glass  tube  upon  the  cloth, 
used  as  a  pad  in  the  pan,  and  fill  with  mercury,  using  the 
funnel.     Half  fill  the  evaporating  dish  with  mercury,  and, 
holding  one  finger  firmly  over  the  open  end  of  the  tube, 
invert   it    in   the    evaporating   dish.     Clamp   the    tube   in 
the  ring  stand.     How  high  does  the  mercury  in  the  tube 
stand  above  the  surface  of  mercury  in  the  evaporating  dish  ? 
Why  is  it  not  30"?     Do  you  think  that  there  is  a  vacuum  at 
the  top  of  the  tube? 


114         INTRODUCTION  TO  GENERAL  SCIENCE 


83.    BOILING  FKOM  ANOTHER  POINT  OF  VIEW 

Section  23  states  that  change  of  state  is  due  to  added  or 
subtracted  molecular  energy,  while  Section  2  states  that  molec- 
ular energy  is  heat.  Since  we  have  just  learned  that  the  at- 
mosphere has  pressure,  we  can  now  look  upon  the  boiling  of 
water  in  a  different  way  from  formerly. 

As  heat  is  added  to  water,  its  molecules  move  faster  and 
faster,  and  those  which  are  near  the  surface  tend  to  pass  away 
into  the  air.  The  molecules  of  the  air,  however,  strike  against 
the  outcoming  water  molecules  and  force  many  of  them  back 
into  the  liquid.  When  the  temperature  of  the  water  becomes 
so  high  that  the  average  velocity  of  the  water  molecules  is 
equal  to  the  average  velocity  of  the  air  molecules,  the  former 
possess  enough  energy  to  overcome  the  atmospheric  pressure, 
and  the  water  boils. 

Since  boiling  is  the  overcoming  of  atmospheric  pressure  by 
the  water  molecules,  if  the  pressure  is  less,  the  water  boils  at  a 
lower  temperature,  for  less  energy  is  necessary.  Therefore 
water  boils  at  a  lower  temperature  on  a  mountain  top  than  in 
a  valley.  The  altitude  may  be  obtained,  approximately,  by 
means  of  a  thermometer.  Using  a  Centigrade  thermometer, 
multiply  the  difference  between  100°  and  the  temperature  at 
which  boiling  begins,  by  295.  This  gives  the  altitude  in 
meters.  With  the  Fahrenheit  thermometer,  multiply  the 
difference  between  212°  and  the  temperature  at  which  boiling 
•  begins,  by  533.  This  gives  the  altitude  in  feet.  Since  cooking 
is  a  chemical  change  due  to  temperature,  a  longer  period  of 
boiling  is  necessary  on  a  mountain  than  at  sea  level  to  accom- 
plish the  same  result. 

In  the  laboratory,  by  means  of  the  air  pump,  water  may  be 


"SUCTION"  115 

made  to  boil  at  any  temperature  between  100°  C.  and  0°  C. 
Ice  may  be  formed  while  the  boiling  continues.     See  Section 
24,  Evaporation  Requires  Heat. 
References :  — 

1.    1803  :  204-206.  Boiling  Point  Defined. 

a.    1309  :  204.  Boiling  at  High  Altitudes. 

6.    1801 :  280-281.     Effect  of  Pressure  on  Boiling  Point. 

c.  1802  :  308.  Ebullition. 

d.  1804  :  281-283.     Boiling  Point. 

e.  1805 :  338-339.     Pressure  and  the  Boiling  Point. 
/.    1807  :  200-202.     Boiling  and  Pressure. 

g.  1808 :  232-233.  Boiling  and  Pressure. 

h.  1809:189-191.  Boiling  and  Pressure. 

i.  1810 : 156-159.  Boiling  Points. 

j.  1811 :  111-112.  Effect  of  Pressure  on  Boiling  Point. 

Experiment  43.  —  Boiling  at  Reduced  Pressure. 

Apparatus:  Glass  flask  250  c.c.,  rubber  stopper  to  fit,  ring 
stand,  asbestos  mat,  burner,  beaker  100  c.c.,  battery  jar  6" 
by  8". 

a.  Put  about  75  c.c.  of  water  into  the  flask,  and  let  it  boil 
vigorously.     While  boiling  insert  the  stopper  and  invert  the 
flask  in  a  ring  of  the  ring  stand.     Place  the  battery  jar  under- 
neath and  pour  a  few  drops  of  water  on  the  inverted  flask. 
What  happens  ?     Continue  to  pour  water  on  the  flask  until 
all  action  ceases.     The  temperature  of  the  inclosed  water  will 
be  about  15°  C. 

b.  Why  was  water  boiled  vigorously  ?    Why  should  only 
a  little  cold  water  be  poured  on  at  first  ?     Why  was  it  difficult 
to  remove  the  stopper  at  the  end  of  the  experiment  ? 

84.    "SUCTION" 

The  quotation  marks  indicate  a  misnomer.  Suction  really 
is  only  half  of  the  process.  The  other  half  is  atmospheric 


116         INTRODUCTION  TO  GENERAL  SCIENCE 

pressure.  If  we  place  a  tube  in  a  liquid,  we  may  suck  the  air 
out  of  one  end  of  the  tube,  but  the  liquid  will  not  come  up  the 
tube  unless  the  atmospheric  pressure  can  act  upon  its  surface. 
Even  if  the  atmospheric  pressure  is  free  to  act  upon  the  surface 
of  water,  the  latter  will  not  rise  more  than  34  feet,  as  that  is 
the  limit  of  the  height  of  a  water  barometer.  See  Section  82, 
Atmospheric  Pressure  and  the  Barometer.  A  rise  of  34  feet 
would  require  that  there  be  a  complete  vacuum  above  the 
water  in  the  tube. 

References :  — 

1.    1803  :  59.  Explanation  of  "Suction.", 

a.    1804 : 167.     Suction. 

Experiment  44.  —  "  Suction." 

Apparatus :  Test  tube  8"  by  I7',  rubber  stopper  with  two 
holes.  Glass  tube  to  fit  one  hole. 

a.  Fill  test  tube  with  water;  insert  stopper.  Placing  finger 
on  the  empty  hole  in  stopper,  suck  on  tube. 

What  happens?  Why?  Remove  finger  and  suck  again. 
Explain. 

85.    PUMPS 

Pumps  are  of  two  classes,  the  lift  pump  and  the  force  pump. 
In  the  lift  pump  the  effec  t  of  atmospheric  pressure  is  made  use 
of;  that  is,  the  action  of  the  pump  is  the  same  as  in  the  case  of 
a  person  who  is  "  sucking  "  on  a  tube.  The  atmosphere  may 
be  said  to  push  on  the  other  end.  A  pump,  then,  if  perfect, 
cannot  lift  water  higher  than  34  feet.  The  usual  pump  can- 
not lift  over  28  feet. 

The  force  pump  may  be  purely  a  force  pump,  in  which  case 
it  is  placed  below  the  surface  of  the  water,  or  it  may  be  a  com- 
bination lift  and  force  pump.  The  height  to  which  a  force 


THE  SIPHON  117 

pump  may  raise  water  is  limited  only  by  the  force  which  is 
applied. 

References :  — 

1.  1803  :  74-75.  The  Lift  and  the  Force  Pump. 

2.  Office  of  Experiment  Stations  101.     Machinery  for  Pumping 

Plants. 

a.    1607  :  546.  The  Suction  Pump. 

6.    1607  :  551-552.  Proper  Place  for  Cylinder  in  the  Well. 

c.  1801 :  127-128.  Air  Pump. 

d.  1804  :  173-174.  The  Lift  and  Force  Pump. 

e.  1805 :  149-151.  The  Lift  and  the  Force  Pump. 
/.    1806:45-46.  Pumps. 

g.  1807  :  44-45.  The  Lift  and  the  Force  Pump. 

h.  1808 :  157.  The  Suction  and  the  Force  Pump. 

i.  1809  :  49-51.  The  Lift  and  Force  Pump. 

j.  1810  :  75-76.  The  Suction  and  the  Force  Pump. 

k.  1811 :  25-38.  Pump  —  Air,  Lift,  and  Force. 

86.    THE  SIPHON 

The  siphon  consists  of  a  bent  tube  with  one  leg  effectively 
longer  than  the  other.  If  such  a  tube  is  placed  in  a  dish  of 
water,  with  the  longer  leg  outside,  and  the  whole  tube  is  filled 
with  water,  the  water  in  the  longer  leg  will  run  out.  This  tends 
to  produce  a  vacuum  in  the  tube,  which  is  prevented  by  the 
atmospheric  pressure,  acting  on  the  surface  of  the  water  and 
pushing  it  up  the  short  leg  of  the  siphon.  Thus  there  is  a 
continual  flow  of  water.  Unless  the  surface  of  the  liquid  in 
the  dish  is  open  to  the  pressure  of  the  air,  the  siphon  will  not 
flow.  The  longer  the  long  leg,  the  faster  the  water  will  flow 
through  the  siphon. 
References :  — 

1.   1803:71-72.  The  Siphon. 

a.   1801:132-134.     The  Siphon. 


118          INTRODUCTION  TO  GENERAL  SCIENCE 

b.  1802:126-128.  The  Siphon. 

c.  1804:170-172.  The  Siphon. 

d.  1805:148-149.  The  Siphon. 

e.  1806  :  45.  The  Siphon. 
/.    1807:45-46.  The  Siphon. 

g.    1808 : 152-153.     The  Siphon  and  its  Action. 
h.    1809:47-49.         The  Siphon. 
i.    1810 :  74-75.         The  Siphon. 

Experiment  45.  —  The  Siphon. 

Apparatus:  Bottle,  wide  mouth,  500  c.c.,  rubber  stopper 
with  two  holes  to  fit,  short  glass  tube  bent  at  right  angles, 
long  glass  tube  bent  at  one  end  so  that  the  shorter  leg  reaches 
the  bottom  of  the  bottle  while  the  other  leg  is  about  three 
feet  in  length.  The  lower  end  should  be  bent  into  a  loop  and 
the  tube  drawn  out  to  form  a  small  tube.  Battery  jar  6"X8". 

a.  Fill  the  bottle  three-fourths  full  of  water,  insert  the 
short  right-angle  tube  in  the  stopper  so  that  one  end  just 
passes  through  it;  insert  the  short  leg  of  the  long  tube  in  the 
other  hole  and  push  the  stopper  into  bottle.     Place    the 
battery  jar  so  as  to  catch  the  water,  and  "  suck  "  on  the  outlet. 
What  happens? 

b.  Place  the  finger  on  the  open  end  of  the  right-angle  tube. 
What  happens?     Why? 

c.  When  the  water  has  passed  out  of  the  bottle,  fill  it  again 
and  devise   some    method  of    starting    the   siphon  besides 
"  sucking." 

87.    NITROGEN  AND  ITS  USES 

Nitrogen  forms  no  chemical  compounds  readily,  and  is  said 
to  be  an  inert  gas.  Its  chief  effect  in  the  atmosphere  is  to 
dilute  the  oxygen.  It  is  probable  that  animals  could  not  live 
in  an  atmosphere  of  pure  oxygen.  Nitrogen  has  also  another 


NITROGEN  AND  ITS   USES  119 

very  important  use  which  has  been  discovered  only  within  the 
last  few  years.  Peas,  beans,  lentils,  alfalfa,  and  a  few  other 
crops  have  on  their  roots  bacteria  which  possess  the  power  of 
absorbing  the  nitrogen  from  the  air,  and  combining  it  with  the 
oxygen  and  some  of  the  salts  of  the  earth  to  form  nitrates. 
These  nitrates  are  very  valuable  as  plant  foods.  If  there  has 
been  a  crop  of  this  kind  in  a  field,  there  is  always  an  excess  of 
bacteria  left  in  the  ground.  These  bacteria  go  on  producing 
the  nitrates  from  the  air,  and  make  the  soil  very  rich.  Thus 
we  know  that  nitrogen  is  used  indirectly  by  plants,  and  that 
these  have  a  never  failing  source  of  plant  food. 

References :  — 

1.  1103  :  7-8.  Nitrogen  in  the  Atmosphere. 

2.  1304 :  229.  Nitrogen  in  the  Atmosphere. 

3.  1407 :  233-235.  Nitrogen  in  Relation  to  Plants. 

4.  1503  :  94-95.  Relation  of  Bacteria  to  Nitrogen. 

5.  1601 :  110-112.  Importance  of  Nitrogen  in  Plant  Life. 

6.  1605  : 116-122.  The  Sources  and  Losses  of  Soil  Nitrogen. 

7.  1702 :  44-45.  Properties  and  Importance  of  Nitrogen. 

8.  1703  :  107-109.  Nitrogen  and  the  Atmosphere. 

9.  1710:6.  Nitrogen. 

a.  1602:45-48.         Clover  and  Other  Plants  take  Nitrogen 

from  the  Air. 

b.  1603  :  33-35.         The  Root  Tubercles. 

c.  1612  : 125-128.     Nitrification  of  the  Soils. 

d.  1701 :  78-80.         Nitrogen  and  its  Properties. 

e.  1706 :  61-64.         The  Atmosphere  and  Nitrogen. 

Experiment  46.  —  To  Prepare  Nitrogen. 

Apparatus:  The  same  as  in  Experiment  3. 

Materials:   Ammonium  nitrite. 

a.  Place  a  teaspoonful  of  ammonium  nitrite  in  the  test 
tube,  add  twice  the  volume  of  water,  and  then  follow  the  direc- 
tions as  given  in  Experiment  3. 


120          INTRODUCTION  TO  GENERAL  SCIENCE 

6.  State  your  conclusions  in  regard  to  nitrogen  as  a  chemi- 
cal element. 

The  nitrogen,  as  prepared  in  this  experiment,  is  pure;  that 
obtained  from  the  air,  in  Experiment  40,  was  very  impure. 

88.    EFFECTS  OF  PAINTING  —  WOOD  PRESERVATION 

Painting  is  looked  upon  more  as  a  matter  of  decoration 
than  as  a  protection  from  the  effects  of  the  weather.  Really, 
however,  beauty  is  a  secondary  consideration,  although  it 
should  not  be  neglected.  Pleasing  combinations  of  tints  and 
shades  are  capable  of  producing  results  which  may  go  far 
toward  making  an  otherwise  ugly  place  appear  attractive. 

Whenever  anything  is  exposed  to  the  oxygen  of  the  air, 
decay  begins.  Moisture  aids  this  disintegration,  as  do  also 
heat  and  cold.  Paint  excludes  both  the  air  and  moisture, 
and  prevents  to  a  great  extent  the  harmful  effects  of  low 
temperature.  All  woodwork  and  metal  work  should  be  pro- 
tected from  the  weather,  and  the  protecting  material  should 
be  carefully  chosen. 

There  is  nothing  equal  to  linseed  oil  as  a  protective  agent. 
In  the  oil  there  should  be  blended  red  lead,  white  lead,  and,  for 
some  purposes,  zinc  white.  Other  oils  and  other  materials 
do  not  produce  equally  lasting  protection  and  should  be  re^ 
jected  where  protection  is  really  desired.  The  color  of  the 
paints  is  a  small  matter,  and  all  paints,  except  red,  are  made 
from  white  paint.  It  is  often  better  to  buy  the  white  paint 
and  color  it  to  suit,  as  it  is  easier  to  detect  foreign  materials  in 
white  paint. 

Wood  can  also  be  preserved  by  creosote  or  by  zinc  chloride. 
Graphite,  applied  to  stoves,  protects  them  like  paint  from 
atmospheric  oxygen. 


EFFECTS  OF  PAINTING  121 

References :  — 

1.  1304 :  42.  The  Protection  Due  to  Paint. 

2.  Forest  Service  Circular  139.     A  Primer  of  Wood  Preservation, 
a.    1706  :  361-362.     Preparation  of  White  Paint. 

6.  1708 :  379.  Preparation  of  White  Paint. 

c.  1709  :  356-358.  Preparation  of  White  Paint. 

d.  1712  :  34.  The  Reason  Why  Paints  Dry. 

e.  1712  :  352-355.  Paints  and  Painting. 

Experiment  47.  —  The  Testing  of  Paint. 
.  Apparatus :  Burner,  blowpipe,  piece  of  charcoal  for  blow- 
piping,  six  beakers  100  c.c.,  small  paint  brush. 

Materials :  Basic  lead  carbonate,  red  lead,  litharge,  whiting, 
barium  sulphate,  zinc  oxide,  linseed  oil,  fish  oil,  kerosene  oil. 

a.  Make  a  little  hollow  in  the  charcoal  and  place  a  small 
amount  of  white  lead  in  it.  Then  direct  the  blowpipe  flame 
against  the  white  lead  so  that  half  of  the  flame  plays  on  it. 
This  reduces  the  white  lead  to  metallic  lead.  Repeat  with 
red  lead  and  litharge.  More  rapid  results  may  be  obtained 
with  these  by  mixing  an  equal  amount  of  ground  charcoal 
with  each  before  blowpiping. 

6.  Repeat  (a)  with  zinc  oxide  and  then  with  barium  sul- 
phate. What  results  do  you  obtain?  Could  you  distinguish 
a  lead  compound  from  zinc  oxide  and  from  barium  sulphate  ? 
These  are  the  chief  adulterants  of  paint.  ^ 

c.  Expose,  in  separate  dishes,  linseed  oil,  fish  oil,  and  kero- 
sene oil  for  twenty-four  hours.     What  is  the  result?    Which 
would  protect  wood  the  best  ?    What  is  the  harm  of  allowing 
paint  to  remain  unused  for  some  time? 

d.  Mix  a  little  white  lead  in  each  of  the  oils  and  see  which 
gives   the   best   blend.     Paint   a   board  with   each   kind   of 
"  paint  "  and  note  the  spreading  ability  of  each. 

e.  Using  linseed  oil,  mix  a  little  zinc  oxide,  paint  the  board, 


122          INTRODUCTION  TO  GENERAL  SCIENCE 

and  examine  in  twenty-four  hours.  Repeat  with  barium 
sulphate  and  whiting. 

Those  who  wish  to  make  an  exact  test  of  paint  may  use  the 
following  method :  — 

To  a  small  amount  of  the  paint  add  ten  times  its  volume  of 
gasoline  and  shake  well.  Allow  solids  to  settle,  pour  off  the 
liquid,  and  repeat  twice.  Collect  ail  of  the  liquid  and  allow 
it  to  evaporate,  or  heat  it  over  water.  Look  out  for  fire. 
After  cooling  the  resulting  oily  residue,  add  a  few  drops  of 
concentrated  sulphuric  acid.  Brown  rings  indicate  linseed 
oil.  Fish  oil  will  not  give  the  same  test,  and  it  may  also  be 
detected  by  its  odor. 

Evaporate  to  dryness  the  solids  which  were  left,  and  add 
acetic  acid.  Both  lead  and  zinc  will  dissolve.  A  residue  indi- 
cates clay  or  barium  sulphate  (barites).  Pass  hydrogen  sul- 
phide (made  by  the  action  of  hydrochloric  acid  upon  ferrous 
sulphide  in  a  hydrogen  generator)  into  the  clear  solution. 
A  black  precipitate  indicates  lead.  Filter,  if  there  is  a 
precipitate,  and  add  ammonium  hydrate.  A  white  precipi- 
tate indicates  zinc. 

89.    CARBON  DIOXIDE 

Carbon  dioxide,  although  existing  usually  in  an  amount 
which  varies  from  three  parts  in  ten  thousand  to  eight  parts  in 
ten  thousand,  nevertheless  possesses  thousands  of  tons  of 
weight.  The  use  of  carbon  dioxide  is  the  maintenance  of 
vegetable  life.  Most  of  the  material  contained  in  trees  and 
coal  once  existed  as  carbon  dioxide  in  the  atmosphere.  Under 
the  effect  of  sunlight,  the  green  coloring  matter  in  the  leaves, 
called  chlorophyll,  has  the  power  of  absorbing  the  carbon 
dioxide,  retaining  the  carbon,  and  giving  forth  the  oxygen. 


CARBON   DIOXIDE  123 

Since  animals  inhale  oxygen  and  exhale  carbon  dioxide,  it 
is  seen  how  nice  is  the  balance  between  animal  life  and  vege- 
table life. 

References :  — 

1.  1103:8-9.  Carbon  Dioxide. 

2.  1304 :  336.  Importance -of  Carbon  Dioxide  to  Plants. 

3.  1407  :  107-108.  Effects  of  Carbon  Dioxide  on  Plants. 

4.  1702  :  66-68.  Carbon  Dioxide  in  Air. 

5.  1703  :  112-113.  Carbon  Dioxide  in  the  Atmosphere. 
1710 :  9-10.  Sources  and  Amount  of  Carbon  Dioxide. 

1302 :  274-275.     Carbon  Dioxide  in  Air. 
1612 :  45-46.          Carbon  Secured  by  the  Leaves  from  Car- 
bon Dioxide. 

c.  1706 :  193-194.      Properties  of  Carbon  Dioxide  and  its  Re- 

lation to  Life. 

d.  1707  :  189-196.     Chemical  Properties  of  Carbon  Dioxide ; 

Respiration. 

e.  1707  :  196-198.     The  Cycle  of  Carbon  in  Nature. 

Experiment  48.  —  Sources  of  Carbon  Dioxide. 

Apparatus:  Funnel,  syringe  bulb  with  inlet  and  outlet 
tubes,  glass  tube  \"  diameter,  8"  long,  test  tube  8"  X  1",  ring 
stand. 

Materials:   Limewater,  candle. 

a.  Place  bulb  between  funnel  and  glass  tube,  put  candle 
under  mouth  of  inverted  funnel,  and  insert  glass  tube  in  test 
tube  containing  5  c.c.  limewater.  Light  candle.  Gently 
force  the  air  from  the  funnel  into  the  limewater,  and  note 
how  quickly  it  becomes  milky. 

6.  Remove  candle,  take  the  apparatus  to  an  open  window, 
and  repeat  process  (without  candle)  with   fresh  and   clean 
limewater.     What  are  your  conclusions  ? 

c.  Remove  funnel  and  gently  breathe  into  some  fresh  lime- 
water.  What  must  you  conclude  ? 


124          INTRODUCTION  TO  GENERAL  SCIENCE 


90.    THE  CHEMICAL  ENGINE 

We  learned  in  Section  5,  Oxygen,  Its  Uses  and  Action, 
that  carbon  dioxide  bombs  are  used  to  extinguish  fires.  Car- 
bon dioxide,  in  solution,  is  also  thrown  upon  fires  in  streams, 
and  the  force  which  the  streams  possess  is  due  to  the  carbon 
dioxide.  This  chemical  is  produced  by  the  action  of  an  acid 
upon  some  carbonate,  which  is  the  combination  of  carbon 
dioxide  and  some  other  element  or  elements.  Where  the 
action  is  to  be  slow,  marble  (calcium  carbonate)  and  sulphuric 
acid  are  used.  If  greater  rapidity  is  desired,  sodium  carbon- 
ate or  sodium  bicarbonate  and  sulphuric  acid  are  used. 

Chemical  engines  are  of  two  kinds  —  the  small  size,  which 
can  be  carried  by  a  man,  and  the  large  size,  mounted  on  a 
carriage  to  be  drawn  by  horses.  The  first  style  cannot  be 
readily  refilled,  but  the  large  size  is  double,  and  one  tank  can 
be  recharged  while  the  other  tank  is  in  operation.  Sodium 
carbonate  is  dissolved  in  the  water  which  fills  the  tank,  and 
a  bottle,  arranged  to  be  inverted  from  the  outside  of  the  tank, 
is  filled  with  sulphuric  acid.  The  tank  is  then  closed,  and  when 
a  stream  is  needed,  the  sulphuric  acid  bottle  is  inverted.  The 
chemical  action  is  very  sudden,  and  the  engine  can  be  used  at 
once.  The  pressure  of  the  gas  drives  out  the  water  with  great 
force.  Considerable  quantities  of  carbon  dioxide  are  held  in 
solution.  When  the  water  reaches  the  fire,  the  chemical  is 
freed  and  excludes  the  oxygen  from  the  combustibles. 

References :  — 

1.    1703  :  192-193.  Preparation  of  Carbon  Dioxide. 

a.  1701 :  206.  Carbon  Dioxide  a  Fire  Extinguisher. 

b.  1704 :  177.  Preparation  of  Carbon  Dioxide. 

c.  1706 :  192-195.  The  Preparation  and  Properties  of  Carbon 

Dioxide. 


OTHER  CONSTITUENTS  OF  THE  ATMOSPHERE      125 

d.  1707 :  192-194.      Preparation   and   Properties    of    Carbon 

Dioxide. 

e.  1709 : 244-246.      Preparation    and    Properties  of    Carbon 

Dioxide. 

Experiment  49.  —  Preparation  of  Carbon  Dioxide  —  the 
Chemical  Engine. 

Apparatus :  Bottle  250  c.c.,  wide  mouth,  rubber  stopper  to 
fit,  with  two  holes,  thistle  tube  with  stopcock,  right-angle  tube, 
one  leg  long  enough  to  reach  the  bottom  of  the  bottle  and  the 
other  leg  drawn  out  to  form  a  small  nozzle. 

Materials :  Sodium  bicarbonate,  hydrochloric  acid  of  full 
strength,  marble. 

a.  Fill  the  bottle  nearly  full  of  cold  water,  and  add  about 
two  teaspoonfuls  of  sodium  bicarbonate.  Insert  thistle  tube 
and  the  right-angle  tube  in  the  two  holes  of  the  stopper,  and 
push  them  in  so  that  they  both  reach  nearly  to  the  bottom  of 
the  bottle.  Shake  the  bottle  gently  until  the  sodium  bicar- 
bonate is  dissolved.  Then  add  hydrochloric  acid,  by  means 
of  the  thistle  tube,  allowing  only  a  little  to  pass  at  a  time. 
Tip  the  bottle  so  that  the  liquid  passes  into  the  sink,  for  if 
the  liquid  touches  skin  or  clothes,  they  will  be  burnt  by  some 
of  the  uncombined  acid. 

6.  Put  a  few  drops  of  half-strength  hydrochloric  acid  upon 
marble.  The  bubbles  are  carbon  dioxide.  If  hydrochloric 
acid  is  placed  upon  any  rock,  and  bubbles  are  formed,  they 
indicate  that  the  rock  is  a  carbonate. 

91.    OTHER  CONSTITUENTS  OF  THE  ATMOSPHERE 

Besides  these  three  principal  ingredients,  oxygen,  nitrogen, 
and  carbon  dioxide,  there  are  several  others,  of  which  dust  and 
bacteria  are  the  most  important. 


126 


INTRODUCTION  TO  GENERAL  SCIENCE 


References :  — 

1.  1103:9. 

2.  1304:230. 

3.  1503:94-95. 

4.  1601:11. 

5.  1702:68-71. 

6.  1703:110-113. 

7.  1710:4. 

8.  1710:16-19. 

9.  1710:40-44. 

a.    1102:47-48. 
6.    1102:159. 

c.  1312:349-351. 

d.  1709:177. 

e.  1903:49-51. 


Microscopical  Impurities  in  the  Air. 
'Other  Constituents  of  the  Atmosphere. 

Relation  of  Bacteria  to  Nitrogen  and  to 
Plants. 

Composition  of  the  Atmosphere. 

Other  Constituents  of  the  Atmosphere. 

Other  Constituents  of  the  Atmosphere. 

Constituents  of  the  Air. 

Substances  in  Suspension  in  the  Air. 

Sources  of  Contamination  of  the  Atmos- 
phere. 

The  Dust  of  the  Atmosphere  —  Colors  of 
the  Sky. 

Dependence  of   Cloud  Condensation  on 
Dust. 

Composition  of  the  Atmosphere. 

The    Carbon-Oxygen   and   the   Nitrogen 
Cycle. 

Bacteria  in  the  Air. 


92.    ATMOSPHERIC  ELECTRICITY 

Lightning  is  the  greatest  manifestation  we  have  of  atmos- 
pheric electricity,  and  the  aurora  is  a  close  second  in  grandeur, 
if  not  in  energy.  The  aurora  may  owe  its  origin  to  the  elec- 
trical energy  which  the  earth  receives  from  the  sun,  but  the 
source  of  atmospheric  electricity  is  not  known,  unless  friction 
causes  it. 

Electrification  is  produced  by  two  different  layers  of  air 
rubbing  upon  each  other;  by  drops  of  water  falling  on  water, 
or  on  a  solid;  and  by  snowflakes  slipping  by  one  another. 
All  these  conditions  increase  their  effect  with  increasing  wind 
velocity.  Nevertheless,  these  effects  all  combined  do  not 
account  for  the  enormous  charges  which  accumulate  in  the 
clouds,  and  which  are  induced  in  the  earth. 


WARMING  THE   AIR  127 

Atmospheric  electricity  is  not  different  from  the  electricity 
which  is  produced  by  friction.  Benjamin  Franklin  showed 
this  by  his  famous  kite  experiment  in  1752.  Since  about 
75,000  volts  are  necessary  to  produce  a  spark  one  inch  long, 
it  can  be  calculated  that  a  flash  of  lightning  over  a  mile  long 
represents  a  voltage  which  cannot  be  comprehended. 

References :  — 

1.  1103:175-179.  Atmospheric  Electricity. 

2.  1304:267-268.  Thunderstorms. 

3.  1803  :  249-250.  Lightning  and  Lightning  Rods. 

4.  Farmer's   Bulletin  No.  367.     Lightning  and  Lightning  Con- 

ductors. 

a.  1102:265-271.  Atmospheric  Electricity. 

b.  1207 : 164-167.  Atmospheric  Electricity. 

c.  1302 : 325-326.  Thunderstorms. 

d.  1303  :  65-66.  Thunderstorms. 

e.  1305  :  106-108.  Atmospheric  Electricity. 
/.  1309  :  275-278.  Atmospheric  Electricity. 

g,  1312  :  395-397.  Electrical  Phenomena  in  the  Atmosphere. 

~\  h.  1801 :  334-336.  Atmospheric  Electricity. 

i.  1804:460-461.  Atmospheric  Electricity. 

j.  1805  :  368.  Lightning  and  Lightning  Rods. 

k.  1808 :  287-290.  Atmospheric  Electricity. 

93.    WARMING  THE  Am 

•Since  the  earth  has  become  cold  on  the  surface,  we  must 
remember  that  all  the  heat  which  we  enjoy  comes  from  the 
sun.  Air  is  heated  in  two  ways,  one  directly,  the  other  in- 
directly; the  greater  amount  of  heat  is  obtained  by  the  in- 
direct method.  We  remember  that  if  a  substance  is  trans- 
parent, the  energy  of  the  sun  passes  through  easily,  and 
therefore  will  not  warm  the  material  through  which  it  passes. 
Since  the  air  is  very  transparent,  the  energy  of  the  sun  passes 


128 


INTRODUCTION  TO  GENERAL  SCIENCE 


through  it  quite  readily;  nevertheless,  some  of  the  energy  is 
stopped,  and  where  any  kind  of  energy  is  stopped,  heat  is 
always  produced.  This  is  the  direct  method  of  heating. 

When  the  sunlight  strikes  the  earth,  which  is  opaque,  all 
of  the  energy  is  stopped,  and  it  is  all  turned  into  heat.  Thus 
the  surface  of  .the  earth  becomes  very  warm.  It  warms  the 
air  above  it  by  conduction;  this  warmed  air  expands  and  is 
pushed  up  by  the  colder  air  on  all  sides,  and  we  say  that  air 
is  becoming  warm  by  convection.  Most  of  the  heat  of  the  air 
is  obtained  in  this  indirect  way.  The  earth  is  prevented,  to  a 
certain  extent,  from  becoming  too  hot  by  the  cold  air  coming 
in  on  all  sides. 


References :  — 

1.  1103:182-183. 

2.  1304:238-239. 

3.  1601:3-4. 

4.  1803:220-221. 

5.  1803:223-224. 
a.    1102:77. 

6.   1301:64-66. 

c.  1303:28-29. 

d.  1306:68-69. 

e.  1307:216-217. 
/.   1310:334-336. 


The  Heat  in  the  Air. 

The  Warming  of  the  Air. 

Air  Warmed  by  Sunshine. 

Warming  of  the  Air  and  Ocean. 

Warming  and  Ventilation  of  Houses. 

The  Motion  Conditions  of  General  Con- 
vection. 

Effect  of  Heat  on  Air. 

Temperature  of  the  Atmosphere. 

General  Circulation  of  the  Atmosphere  Due 
to  Heat. 

Effects  of  Temperature  on  the  Air. 

The  Heating  of  the  Atmosphere. 


94.    WINDS 

Air  in  motion  is  wind.  The  air  has  a  definite  weight,  which 
produces  the  pressure  of  about  fourteen  and  seven  tenths 
pounds  per  square  inch,  or  about  one  ton  per  square  foot,  on 
the  entire  surface  of  the  earth.  If  the  air  ill  one  section  is 


KINDS  OF   WINDS  129 

warmed,  it  expands,  and,  becoming  lighter,  is  shoved  upward 
by  the  air  flowing  in  from  all  directions  to  take  its  place.  This 
produces  the  winds,  and  no  matter  what  kind  of  winds  they 
may  be,  they  are  all  produced  in  the  same  way. 

References :  — • 

1.  1103  :  73-80.  Air  Pressure. 

2.  1103  :  180-192.  General  Circulation  of  the  Atmosphere. 

3.  1304 :  255-262.  Winds  of  the  Earth. 

4.  1601 :  4.  Winds  Caused  by  Sunshine. 

5.  1803  :  58-63.  Pressure  in  Air. 

a.  1102 : 11-14.  Pressure  and  Extent  of  the  Atmosphere. 

b.  1102 :  82-85.  Measurement  of  Atmospheric  Pressure. 

c.  1301 :  85-90.  Air  Pressure. 

d.  1303  :  24-26.  Pressure  of  the  Atmosphere. 

e.  1305  :  78-89.  Movements  of  the  Atmosphere. 
/.  1306:83-84.  The  Nature  of  Winds. 

g.    1307  :  214-225.     The  Atmosphere  and  Winds. 

h.    1308 :  94-99.        Movements  of  the  Atmosphere  —  Winds. 

i.    1804 : 155-163.     Atmospheric  Pressure. 

95.    KINDS  OF  WINDS 

All  general  breezes  of  the  earth  are  caused  by  the  air  of  the 
equator  being  hotter  than  the  air  at  the  poles.  These  breezes, 
or  winds,  are  called  terrestrial  winds,  and  are  divided  into 
four  classes,  starting  from  the  equator,  — «•  the  doldrums,  the 
trades,  the  prevailing  westerlies,  and  the  circumpolar  whirls. 
There  are  local  breezes  called  the  sea  breeze  and  land  breeze, 
the  day  breeze  and  the  night  breeze,  the  mountain  breeze 
and  the  valley  breeze;  but  they  are  all  based  upon  the  same 
principle.  The  land  and  sea  breezes  may  be  taken  as  ex- 
amples for  explanation. 

In  the  daytime  the  land  becomes  warm  faster  than  the 
ocean,  because  the  land  is  opaque  and  stops  the  energy  of  the 
I 


130          INTRODUCTION  TO  GENERAL  SCIENCE 

sun.  The  ocean  is  transparent  and  allows  some  of  the  energy 
to  pass  through.  There  are  also  convective  currents  in  the 
ocean  which  cause  much  of  the  water  to  be  raised  to  the  same 
temperature,  while  it  is  only  the  surface  of  the  earth  that  is 
warmed.  Therefore  the  air  over  the  land  becomes  much 
hotter  than  the  air  over  the  water,  expands,  and  is  pushed  up 
by  the  colder  air  coming  in  from  the  ocean.  This  produces 
the  sea  breeze.  In  the  night  the  land  cools  off  faster  than 
the  ocean,  because  water,  owing  to  its  great  capacity  for  heat, 
retains  heat  -longer  than  any  other  substance.  Then  the  air 
over  the  ocean  is  warmer  than  over  the  land,  and  the  cooler 
air  of  the  land  goes  out  to  take  the  place  of  the  warmer  air 
over  the  ocean. 

References :  — 

1.  1103 : 101-104.  The  Winds  of  the  Globe. 

2.  1304 :  255-262.  Different  Kinds  of  Winds. 

a.  1102  :  112-139.  All  the  Kinds  of  Winds. 

b.  1301 :  90-100.  Planetary  Winds. 

c.  1302  :  304-311.  The  Relations  of  Pressure  and  Winds. 

d.  1305  :  81-89.  Three  Classes  of  Winds. 

e.  1306  :  70-84.  Classification  of  the  Winds. 

/.    1308 :  94-99.  Movements  of  the  Atmosphere. 

g.    1309 :  218-225.  Atmospheric  Circulation. 

h.    1310 :  386-396.  General  Circulation  of  the  Atmosphere. 

i.    1311 :  266-268.  Origin  of  Terrestrial  Winds. 

j.   1312 :  368-370.  Classification  of  the  Winds. 

k.   1313:185-188  Kinds  of  Winds. 

96.    VELOCITY  OP  WINDS 

The  velocity  of  winds  depends  upon  the  difference  of  tem- 
perature in  the  place  from  which  the  wind  comes  and  the  place 
toward  which  the  wind  is  going.  The  greater  the  difference 
of  temperature  between  the  two  places,  the  greater  the  veloc- 


RESOLUTION  OF  FORCES  131 

ity  of  the  wind.  It  also  depends  upon  certain  whirls  in  the 
atmosphere,  which  are  not  very  well  understood,  but  which 
will  be  discussed  when  we  consider  the  weather  and  its  causes. 
The  recording  of  weather  changes,  including  the  measurement 
of  wind  velocity,  is  given  in  Section  109,  Weather  Instru- 
ments. 

References :  — 

1.  1103  :  106-113.  Variation  in  the  Velocity  of  the  Winds. 

2.  1304 :  422.  Anemometer,  or  Wind  Measurer. 

a.    1102  :  ^4-95.         Force  and  Velocity  of  the  Wind  and  its 

Measurement. 
6.    1301 :  99-101.       Velocity  of  Wind. 

c.  1302  :  288-289.      Pressure  and  Velocity  of  Winds. 

d.  1303  :  37-38.         Observation  of  Winds. 

e.  ,1309  :  218.  Winds  and  their  Measurements. 

/.    1312  :  376.  High  Velocity  of  Winds  from  Tornadoes. 

g.    1607 :  532.  Relation  of  Wind  Pressure  to  Wind  Veloc- 

ity. 


97.    RESOLUTION  OF  FORCES 

In  Section  38  we  learned  that  each  force  acts  independently 
of  all  other  forces  which  may  be  acting  at  the  same  time.  We 
also  learned  that  the  result  obtained  by  two  forces  could  be 
accomplished  by  one  force  properly  directed.  It  will  not 
seem  strange,  then,  to  learn  that  any  force  may  be  resolved, 
or  analyzed,  into  two  or  more  components.  The  components 
usually  desired  are  the  two  forces,  which,  acting  at  right  angles, 
could  produce  the  single  force  under  consideration.  These 
forces  may  be  obtained  geometrically  or  graphically. 

The  given  force  should  be  considered  as  the  hypotenuse  of 
a  right  triangle.  The  other  forces,  that  is,  the  components, 
are  the  base  and  altitude  of  the  right  triangle.  Since  an  in- 


132          INTRODUCTION  TO  GENERAL  SCIENCE 

finite  number  of  triangles  can  be  constructed  upon  a  given 
line,  any  combination  of  two  forces  may  be  obtained  which 
are  at  right  angles  to  each  other. 

Any  force  which  is  not  applied  in  the  direction  of  the  de- 
sired movement  has  a  component  of  loss.  Thus  the  traces 
of  a  harness  should  be  as  nearly  parallel  to  the  ground  as  pos- 
sible, and  the  tow  rope  of  a  towboat  should  be  moderately 
long  to  avoid  the  sidewise  pull.  Similarly,  a  sprinter  in 
starting  should  keep  his  "  push-off  "  leg  parallel  to  the  ground. 

References :  — 

1.    1803  :  14-19.  Composition  and  Resolution  of  Forces, 

a.    1607 :  492-493.  The  Best  Position  of  the  Traces  of  a  Har- 
ness. 

6.    1801 :  42.  Resolution  of  a  Force. 

c.  1802  :  80-81.  Resolution  of  Forces. 

d.  1804 :  62.  Resolution  of  Forces. 

e.  1805  :  44-47.  Resolution  of  Forces. 

/.  1806 :  116-117.  Composition  and  Resolution  of  Forces. 

g.  1807  :  54.  Resolution  of  a  Force. 

h.  1808 :  46-47.  Resolution  of  Forces. 

•  i.  1809  :  74-79.  Composition  of  Forces. 

j.  1810  :  53-55.  Resolution  of  Forces,  Velocities,  and  Accel- 
erations. 

k.  1811 :  366-369.  The  Resolution  of  Forces. 

Experiment  50.  —  Resolution  of  Forces. 

Apparatus :  Block  of  wood  6"  X  3"X  J",  set  of  weights,  spring 
balance,  protractor,  board  3'X5"Xf"  with  a  narrow  strip  of 
wood  nailed  along  one  edge,  two  thumb  tacks,  string. 

a.  Drive  a  nail  in  the  center  of  the  flat  side  of  the  6"X3" 
block,  and  fasten  the  protractor  with  thumb  tacks  so  that  its 
diameter  lies  lengthwise  of  the  block,  its  center  point  against 
the  nail.  Tie  a  string  to  the  nail  and  make  a  loop  at  its  end 
for  the  spring  balance.  Place  the  block  on  the  long  board, 


THE  THEORY  OF   THE   KITE  133 

against  the  strip,  and  weight  it  until  there  is  a  definite  pull, 
when  the  balance  is  drawn  along  with  a  uniform  motion. 

b.  What  is  the  pull  when  the  balance  is  drawn  lengthwise 
of  the  board  ?  This  is  the  total  force  which  is  necessary  to 
move  the  block  with  its  load  of  weights.  Now  draw  the 
balance  a  little  toward  the  strip  so  that  the  string  crosses  the 
protractor  at  an  angle  of  5°  from  the  line  of  the  block's  mo- 
tion. What  pull  is  necessary?  What  has , happened  to  the 
extra  force?  Increase  the  size  of  the  angle,  and  note  the 
increasing  loss  of  force.  A  pull,  or  a  push,  at  an  angle  to 
the  desired  direction  of  motion,  has  a  component  of  loss. 

98.    THE  THEORY  OF  THE  KITE 

With  the  kite  it  is  necessary  to  resolve  the  force  of  the  wind, 
which  blows  for  the  most  part  parallel  with  the  earth's  surface, 
into  two  forces.  One  must  act  at  right  angles  to  the  surface 
of  the  kite,  as  the  effective  force,  and  the  other  parallel  to  the 
surface  of  the  kite,  though  not  affecting  the  latter.  The  per- 
pendicular force  must  then  be  resolved  into  two  forces,  one 
acting  parallel  to  the  string,  producing  the  "  pull  "  of  the  kite, 
and  the  other  acting  at  right  angles  to  the  string,  producing 
the  lifting  of  the  kite  itself.  By  regulating  the  angle  at  which 
the  string  leaves  the  kite,  the  latter  may  -be  made  a  "  puller  " 
or  a  "  high  flyer."  The  more  the  top  of  the  kite  is  inclined 
toward  the  string,  the  higher  the  kite  will  fly  until  the  limit  of 
height  for  that  kite  is  reached. 

Kites  may  be  balanced  by  means  of  a  tail  or  by  so  shaping 
the  surface  of  the  kite  that  it  sheds  the  wind  equally  from  the 
two  sides.  The  Malays  have  evolved  this  style,  and  it  is  the 
best  for  simple  construction.  The  box  kite,  which  consists 
of  two  or  more  cells  into  which  the  wind  blows,  is  more  com- 


134          INTRODUCTION  TO  GENERAL  SCIENCE 

plicated,  but  has  a  greater  lifting  power.  Kites  are  used  for 
observational  purposes,  usually  in  war,  and  to  obtain  data 
concerning  the  conditions  of  the  upper  atmosphere. 

Reference :  — 

1.    1803  :  249.     Franklin's  Kite. 

Experiment  51.  —  To  Make  a  Malay  Kite. 

Materials:  Two  sticks  5'X^'Xj",  string,  light  paper,  flour 
paste. 

a.  Cross  the  two  sticks  at  the  middle  point  of  one,  one  fifth 
its  length  from  an  end  of  the  other,  and  bind  together.  Slot 
the  ends  of  the,  sticks  and  run  a  string  around  the  kite  frame. 
Paper  the  kite,  turning  over  as  small  a  margin  as  is  convenient, 
say  one  inch,  and  paste  with  boiled  flour  paste.  The  bridle 
should  be  fastened  at  the  crossing  of  the  sticks  and  at  the  lower 
end  of  the  upright  stick,  and  the  loop  should  be  about  eight- 
een inches  from  the  kite.  Tie  a  string  at  one  end  of  the 
horizontal  stick,  and  then  bend  this  stick  backward  so  that 
when  its  other  end  is  tied  by  the  string  the  distance  between 
the  string  and  the  crossing  of  the  sticks  will  be  one  fifth  the 
length  of  the  stick.  To  fly  the  kite,  tie  a  loop  in  the  bridle 
at  such  a  place  as  will  cause  the  kite  to  fly  high  or  low,  as 
desired.  This  point  can  be  determined  by  holding  the  kite 
by  its  bridle  in  the  wind.  If  not  satisfactory,  adjust  again, 
as  practice  and  theory  must  go  hand  in  hand. 

The  author  has  devised  a  kite  which  makes  use  of  curved 
surfaces.  Because  of  the  curves  it  is  hard  to  paper,  although 
with  care  this  can  be  accomplished.  A  cloth  .covering  is 
preferable,  as  it  is  in  all  kites  larger  than  5'X5'.  This  design 
may  be  made  in  the  following  manner :  — 

Take  two  sticks  (white  cedar  wood  is  best)  1.5  cm.X.7  cm. 
tapered  to  1  cm.X.4  cm.,  110  cm.  long,  and  lash  them  together 


THE  THEORY  OF  THE  AEROPLANE  135 

at  right  angles,  allowing  the  thicker  ends  to  project  2  cm.  The 
smaller  ends  of  these  two  sticks  are  lashed  to  the  ends  of  a 
third  stick,  1  cm.  X  .7  cm.,  tapered  to  1  cm.  X  .4  cm.  at  each 
end,  170  cm.  long,  for  a  distance  of  20  cm.  from  each  end. 
This  forms  a  triangle  with  all  three  sides  bending  in.  Now 
strongly  lash  the  ends  which  project  2  cm.  to  a  stick  1.5 
cm.  XI. 5  cm.,  tapered  to  1.5 X. 7  cm.,  170  cm.  long  7  cm. 
from  the  larger  end.  Tie  a  string,  at  its  middle  point,  to  the 
smaller  end  of  this  last  stick,  having  the  two  ends  of  the  string 
long  enough  to  reach  the  outer  ends  of  the  cross  sticks;  pull 
down  the  ends  of  the  cross  sticks  equally  until  a  line  joining 
their  two  extremities  is  135  cm.  distant  from  the  bottom  of 
the  kite.  Paper  the  kite  by  fitting  the  paper  over  the  string 
first,  covering  the  cross  sticks  last.  Leave  the  paper  quite 
loose.  Fasten  the  bridle  as  in  the  Malay  kite. 

If  this  kite  is  made  so  that  it  balances  and  sheds  the  wind 
equally  from  both  sides,  it  may  be  so  hung  that  it  will  fly  at  a 
very  slight  angle  from  the  vertical.  If  for  any  reason  the 
kite  comes  down,  it  lands  like  a  bird,  without  damage  to  itself. 

99.    THE  THEORY  OF  THE  AEROPLANE 

The  aeroplane  consists,  essentially,  of  a  plane,  or  planes. 
It  is  forced  through  the  air  by  means  of  powerful  propellers, 
differing  but  slightly  from  electric  fans.  The  theory  of  the 
aeroplane  is  very  similar  to  that  of  the  kite.  In  the  case  of 
the  kite  the  plane  stays  still  and  the  wind  goes  by;  with  the 
aeroplane  the  air  may  be  stationary,  but  the  plane  moves.  In 
both  cases  there  is  a  component  of  the  total  force  which  is 
opposed  to  gravity,  and  the  kite  and  the  aeroplane  rise,  al- 
though both  are  heavier  than  air.  There  must  be  motion 
between  the  planes  and  the  air  in  both  cases. 


136         INTRODUCTION  TO  GENERAL  SCIENCE 

It  must  be  remembered  that  the  complete  theory  of  the 
aeroplane,  or  even  of  the  kite,  is  much  more  complex  than 
has  been  stated,  and  many  other  factors  enter  into  considera- 
tion. It  might  be  well  to  state  that  the  effective  area  of  a 
plane  increases  with  the  velocity,  since  the  air  is  forced  more 
to  the  sides;  and  curved  planes  give  a  greater  component  of 
lift,  due  partly  to  reaction. 

Reference :  — 
a.     1809  :  79.     The  Aeroplane. 

Experiment  52.  —  To  Make  a  Boomerang. 

Materials:   Piece  of  pasteboard  6"  square. 

a.  Cut  from  the  pasteboard  a  piece  similar  to  a  carpenter's 
square,  having  both  sides  six  inches  long  and  one  and  one  half 
inches  wide.  Round  the  ends  so  that  they  are  semicircles, 
and  round  the  outside  angle,  formed  by  the  two  sides,  so  that 
it  is  a  quarter  circle. 

6.  Place  the  boomerang  on  a  book  so  that  one  end  points 
toward  you  and  the  other  end  projects  at  right  angles  to  the 
edge  of  the  book.  Incline  the  latter  at  an  angle  of  30°  from 
the  horizontal,  and  hit  the  projecting  end  of  the  boomerang 
a  smart,  straight  blow  with  a  pencil. 

After  a  few  trials  the  boomerang  can  be  made  to  go  some 
distance  away  and  upwards,  and  then  return  to  the  feet  of  the 
operator. 

This  toy  illustrates  the  first  law  of  motion,  in  that  it  main- 
tains its  motion,  revolving  continually  in  the  same  plane. 
The  aeroplane  glides  through  the  air,  and  is  prevented  from 
falling  to  earth,  and,  in  fact,  leaves  the  earth,  by  means  of  its 
inclined  planes,  in  much  the  same  way  as  the  boomerang 
behaves. 


SAILING  A  BOAT  137 


100.    SAILING  A  BOAT 

The  kite  and  the  aeroplane  both  act  in  a  single  medium; 
that  is,  they  move  in  air  only.  A  sailboat  moves  in  water,  but 
obtains  its  energy  from  the  motion  of  the  air.  The  theory  of 
sailing  a  boat,  however,  does  not  greatly  differ  from  the  theory 
of  the  kite. 

The  force  of  the  wind,  as  it  strikes  against  the  sails,  may  be 
resolved  into  one  component  perpendicular  to  the  sail,  and 
into  another  component  parallel  to  the  sail.  The  latter  has 
no  effect  if  the  sail  is  flat.  The  perpendicular  component  can 
be  resolved  into  'one  component  acting  in  the  direction  of  the 
boat's  motion,  which  tends  to  send  the  boat  ahead,  and  into 
another  component  acting  at  right  angles  to  the  boat's  motion. 
This  causes  leeway  and  may  be  prevented  to  some  extent  by 
a  deep  keel,  or  by  a  centerboard. 

The  windmill  acts  very  similarly  to  a  sailboat  when  the 
latter  is  sailing  across  the  breeze,  with  the  exception,  of  course, 
that  the  windmill  is  constrained  to  revolve. 

It  may  be  well  at  this  point  to  state  again  that  this  theory 
is  only  part  of  the  whole  theory  and  does  not  take  into  con- 
sideration the  fact  that  with  sails  of  boats  and  with  blades  of 
windmills  the  curved  surface  plays  a  prominent  part  in  the 
production  of  motion.  Reaction  also  enters  into  the  problem 
of  transforming  the  energy  of  the  wind  into  useful  work. 

References :  — 

a.  1607:531-534.  The  Windmill. 

b.  1804:63.  The  Theory  of  Sailing. 

c.  1809  :  78-79.  Boat  Sailing. 

d.  1811:368-369.  The  Theory  of  Sailing. 


138         INTRODUCTION  TO  GENERAL  SCIENCE 

Experiment  53.  —  To  Make  a  Windmill. 

Materials :  Piece  of  paper,  eight  inches  square,  pin. 

a.  Fold  the  paper  diagonally  twice,  then  tear,  or  cut,  along 
the  diagonals  two  thirds  the  distance  from  the  corners  to  the 
center.  Fasten  alternate  corners  to  the  center  with  a  pin. 
This  produces  a  four-blade  windmill  which  will  revolve  in  the 
current  of  air  produced  by  a  person  while  walking.  Such 
wind  wheels  may  be  made  double,  or  of  any  number  of  sheets, 
and  in  colored  paper  be  used  for  purposes  of  decoration. 

101.    HUMIDITY 

In  addition  to  the  various  gases  which  compose  the  atmos- 
phere, there  is  a  varying  quantity  of  water  vapor,  which  is  the 
most  important  substance.  Without  this  water  vapor  there 
could  be  no  growth  of  vegetation,  for  there  could  be  no  rain 
under  any  circumstances.  Water  exists  in  several  states;  it 
appears  as  clouds,  fog,  mist,  rain,  dew,  frost,  snow,  hail,  and 
ice.  Water  vapor  is  invisible. 

The  water  vapor  makes  the  air  damp,  although  it  does  not 
affect  the  amount  of  air  which  is  present.  That  is,  water 
vapor  does  not  crowd  out  the  air,  and,  on  the  other  hand,  no 
more  water  vapor  would  be  present,  under  given  conditions  of 
temperature  and  pressure,  if  the  air  were  wholly  removed.  . 

Sulphuric  acid  has  the  power  of  absorbing  water,  and  an 
open  dish  of  this  acid  is  used  to  remove  the  moisture  from 
within  clock  and  balance  cases,  in  order  to  prevent  the  rusting 
of  delicate  parts.  Such  a  dish  of  acid,  if  exposed  to  the  open 
air,  rapidly  gains  in  weight,  due  to  the  water  which  is  absorbed 
from  the  air. 

The  total  amount  of  water  vapor  which  the  air  can  hold 
under  given  conditions  is  called  saturated  humidity;  the 


DEW  139 

total  amount  which  the  air  does  hold  is  called  absolute  hu- 
midity. The  absolute  humidity  divided  by  the  saturated 
humidity  is  called  relative  humidity.  It  is  the  latter  which 
concerns  us.  The  higher  the  temperature,  the  more  water  can 
exist  as  vapor;  therefore  warming  a  house  seems  to  dry  it, 
although  the  same  amount  of  water  may  be  present  as  when 
it  was  cold.  The  relative  humidity  should  be  between  70 
per  cent  and  75  per  cent.  A  further  consideration  of  hu- 
midity will  be  studied  in  Section  190,  Dangers  of  Vitiated  Air, 
in  connection  with  ventilation. 

References :  — 

1.  1103:122.  Atmospheric  Humidity. 

2.  1304:244-245.  Humidity. 

3.  1803  :  100.  Humidity  of  the  Atmosphere. 
a.   1102:144-146.  Humidity. 

6.  1302:281-282.  Humidity. 

c.  1303:60-61.  Humidity. 

d.  1305:66-68.  Humidity. 

e.  1308 :  93.  Humidity  and  its  Condensation. 
/.  1309:239.  Humidity. 

g.  1310:364-366.  Humidity. 
h.  1311:226-227.  Humidity. 
i.  1312  :  379-380.  Absolute  and  Relative  Humidity. 

EXPERIMENT  FOR  THE  TE'ACHER 
Moisture  in  the  Air 

Expose  a  thin  layer  of  sulphuric  acid  (concentrated)  in  a 
large  open  glass  dish.  Weigh  before  and  after  exposure  of 
twenty-four  hours. 

102.    DEW 

There  is  an  old  saying  that  dew  falls,  but  this  is  not  the 
truth,  since  the  dew  is  formed  at  the  place  where  it  appears. 


140         INTRODUCTION  TO  GENERAL  SCIENCE 

Water  vapor,  when  cooled  to  its  point  of  saturation,  called 
the  dew  point,  condenses  into  liquid  water.  Due  to  radia- 
tion, the  surface  of  the  ground,  and  especially  the  vegetation, 
becomes  cool  after  sunset,  and  rapidly  lowers  the  temperature 
of  the  surrounding  air.  This  causes  the  invisible  water  vapor 
to  condense  as  dew. 

Whenever  water  vapor  condenses,  it  gives  out  large  quan- 
tities of  heat,  as  we  have  learned  in  the  case  of  condensation 
of  steam  in  Section  25.  If  water  vapor  condenses  at  a  lower 
temperature  than  100°  C.,  it  gives  out  more  heat  than  it  does 
at  the  boiling  point.  Each  gram  of  water  vapor,  when  it  con- 
denses, gives  out  a  number  of  calories  which  can  be  estimated 
roughly  by  multiplying  the  temperature  by  six  tenths  and 
subtracting  this  result  from  596.  For  the  above  reason,  if 
the  relative  humidity  is  great,  the  temperature  will  remain 
more  constant  during  the  night  than  it  would  if  the  air  were 
very  dry. 

References :  — 

1.  1103  : 123-124.  The    Dew  Point   and   the  Measurement 

of  Humidity. 

2.  1103:162.  Dew. 

3.  1304:246.  Dew. 

4.  1803  : 97-99.  Condensation  of  Water  from  the  Air. 

5.  Weather  Bureau  Bulletin  No.  235.     Psychrometric  Tables. 

a.  1102  :  155-157.  Formation  of  Dew  and  Frost. 

b.  1301 :  130-131.  Dew  and  its  Formation. 

c.  1302  :  285-286.  Dew  and  Frost. 

d.  1303  : 61-62.  Dew  and  Frost. 

e.  1305  :  75.  Natural  Formation  of  Dew. 
/.  1306:107-108.  Dew. 

g.  1307 :  232-234.  Dew  Point  and  Dew. 

h.  1309:241-242.  How  Dew  is  Formed. 

i.  1310 :  372-373.  Dew  and  Frost. 

j.  1311:227-228.  Dew  and  Frost. 


FROST  141 

Experiment  54.  —  Dew  Point. 

Apparatus:  Small,  brightly  polished,  nickel-plated,  cy- 
lindrical brass  dish  1"  X  3"  (a  shaving-stick  box  is  excellent, 
for  this  purpose),  rubber  stopper  with  three  holes,  to  fit,  ther- 
mometer, all  glass,  right-angle  glass  tube,  syringe  bulb, 
rubber  tubing,  ring  stand. 

Materials:   Ether. 

a.  Fill  brass  tube  one  third  full  of  ether,  push  the  ther- 
mometer into  one  hole,  the  right-angle  tube  into  a  second  hole, 
of  the  stopper,  and  insert  it  in  the  top  of  the  brass  tube.     At- 
tach the  syringe  bulb,  by  means  of  rubber  tubing,  to  the  right- 
angle  tube.     Support  the  brass  tube  by  its  stopper. 

b.  By  means  of  the  bulb  cause  air  to  pass  through  the 
ether,  taking  care  not  to  breathe  on  the  tube.     The  tempera- 
ture falls  rapidly,  and  soon  moisture  will  begin  to  collect  on  the 
outside  of  the  brass  tube.     Stop  forcing  air  in,  and  read  the 
thermometer.     Wait  until  the  moisture  disappears,  and  read 
the  thermometer  again.     The  average  of  the  two  readings  is 
the  dew  point. 

c.  Repeat  this  experiment  early  some  morning. 
Knowing  the  dew  point  and  the  temperature,  the  relative 

humidity  may  be  discovered  by  means  of  tables.     See  ref- 
erences. 

103.    FROST 

Frost  is  formed  in  much  the  same  way  as  dew,  although  in 
this  case  the  formation  takes  place  below  the  freezing  point 
of  water,  which  is  32°  Fahrenheit.  The  invisible  water  vapor 
passes  directly  from  the  gaseous  state  to  the  solid  state,  with- 
out any  intermediate  stage.  If  the  wind  is  blowing  on  a  cold 
night,  there  will  be  very  little  frost,  and  perhaps  none  at  all, 
because  as  fast  as  the  air  is  cooled  more  air  comes  in;  thus  the 


142         INTRODUCTION  TO  GENERAL  SCIENCE 

temperature  of  any  particular  section  of  the  air  is  not  lowered 
below  its  freezing  point.  Again,  if  there  is  much  fog,  there 
will  be  no  frost,  since  the  formation  of  the  fog  raises  the  tem- 
perature of  the  air.  However,  where  the  air  has  very  little 
water  vapor,  we  may  have  what  is  called  a  black  frost,  which 
merely  means  that  the  water  in  the  plants  themselves  is  actu- 
ally frozen,  and  when  this  thaws  out,  they  wilt  and  die.  This 
will  explain  the  peculiar-  statement  which  people  make, 
namely,  that  after  a  cold  night  it  is  the  sun  which  destroys  the 
flowers. 

References:  — 

1.  1103:290-291.  Frost. 

2.  1304:246.  Frost. 

3.  Farmers'  Bulletin  No.  104.     Notes  on  Frost. 

a.  1101 :  135.  Formation  of  Frost. 

b.  1102  : 156-158.  Frost  and  its  Prediction. 

c.  1301 :  132.  Frost  and  its  Formation. 

d.  1302  :  285-286.  Dew  and  Frost. 

e.  1305:75.  Hoarfrost. 
/.  1306:108.  Frost. 

g.  1310 :  367-368.  Fog,  Frost,  and  Cloud. 

h.  1311:227-228.  Dew  and  Frost.  • 

i.  1312  :  381-382.  Dew  and  Frost. 

j.  1807 : 199.  Conditions  for  Frost. 

104.    FOG  AND  CLOUDS 

These  two  are  very  much  the  same,  the  fog  being  either  at 
the  surface  of  the  earth  or  a  little  above  it,  while  the  clouds 
are  usually  half  a  mile  or  more  high.  The  conditions  which 
cause  their  production  are  very  similar:  a  warm  mass  of  air 
carrying  large  quantities  of  water  vapor  is  cooled,  for  various 
reasons,  which  causes  the  water  vapor  to  condense  into  a  great 
many  minute  drops  which  form  the  fog  or  clouds. 


SNOW  AND    HAIL  143 

References :  — 

1.  1103:129-137.  Formation  of  Fog  and  Clouds.     Classifi- 

cation of  Clouds. 

2.  1304 :  247-248.          Fog  and  Clouds. 

3.  Weather  Bureau.     Classification  of  Clouds.    With  Chart. 

a.  1102:  158-159.  Fog  and  the  Cause  of  Condensation. 

b.  1301 :  133-140.  Fog  and  Clouds. 

c.  1303  :  62-64.  Clouds,  Fogs,  and  Mist. 

d.  1305  :  68-70.  Fog  and  Clouds. 

e.  1306:169-174.  Fog  and  Clouds. 

/.  1307  :  235-238.  Clouds  and  their  Nomenclature. 

g.  1311 :  228-231.  Fog  and  Clouds. 

h.  1309  :  242-247.  Fog  and  Clouds. 

i.  1310 :  367-373.  Cloud,  Dew,  and  Frost. 

j.  1312:382-385.  Clouds. 

105.    SNOW  AND  HAIL 

Snow  is  not  frozen  rain,  but  may  be  considered  as  aerial 
frost.  Snow  is  formed  where  water  vapor  is  cooled  so  sud- 
denly that  it  passes  directly  from  the  vapor  state  into  the 
solid  state,  without  any  intermediate  liquid  state.  That  is, 
the  formation  of  snow  is  an  example  of  sublimation.  Snow 
crystals  are  very  beautiful  and  are  of  many  varieties,  although 
all  are  six-sided,  or  six-spoked,  at  angles  of  60°. 

Hail  is  frozen  rain.  The  formation  of  the  larger  hailstones 
requires  quite  a  long  period  of  time  and  many  ascents  and 
descents  before  they  finally  fall  to  the  ground.  The  rain 
falls  through  a  layer  of  cold  air  and  is  partly  frozen;  then 
other  currents  of  air  force  the  tiny  hailstones  back  into  the 
colder  layer  of  air,  where  they  grow  by  the  addition  of  more 
freezing  water.  This  process  continues  until  the  ascending 
currents  cannot  sustain  the  increasing  weight  of  the  hailstones, 
which  then  fall  for  the  last  time.  Much  damage  to  windows 


144         INTRODUCTION  TO  GENERAL  SCIENCE 

and  to  crops  may  be  caused  by  the  larger  hailstones,  which 

sometimes   measure  as   much   as   two   to  three  inches  in 
diameter. 
References :  — 

1.  1103  : 159.  Hail  and  Snow. 

2.  1304 :  249-250.  Snow  and  Hail. 

3.  1803  :  99.  The  Formation  of  Clouds,  Rain,  Hail,  and 

Snow. 

4.  Weather  Bureau.      Photomicrographs  of  Snow  Crystals. 

a.  1102  :  286-287.  Snow  and  Hail. 

b.  1302  :  284-285.  Snow  and  Hail. 

c.  1303  :  70.  Snow  and  Hail. 

d.  1305 :  72-73.  Snow  and  Hail. 

e.  1309  :  258-259.  Hail  and  Snow. 
/.  1807 :  200.  Snow  and  Hail. 

Experiment  55.  —  Sublimation. 

Apparatus:    Burner,  test  tubes  6"Xf",  test-tube  holder, 
stirring  rod  of  glass. 

Materials :    Ammonium  chloride,  iodine,  alcohol. 

a.  Place  a  quarter  teaspoonful  of  ammonium  chloride  in  a 
test  tube  and  heat  it.     Does  the  ammonium  chloride  melt  ? 
Stick  the  rod  into  the  test  tube  for  a  minute,  then  remove  the 
tube  from  the  burner.     Examine  the  rod.     What  has  hap- 
pened ? 

b.  Repeat,  using  a  few  grains  of  iodine.     What  is  the  color 
of  iodine  ?     Of  the  vapor  of  iodine  ?     Describe  the  result. 

c.  Dissolve  the  iodine  with  alcohol.     State  the  difference 
between  melting  a  substance  and  dissolving  it  in  some  solvent. 

106.    RAINFALL  —  CYCLONES 

If  the  cooling  of  the  warm  air  is  carried  beyond  the  forma- 
tion of  clouds,  there  will  be  so  much  water  condensed  that  it 


RAINFALL  145 

can  no  longer  float,  or,  to  say  the  same  thing  in  other  words, 
the  particles  or  little  drops  of  water  will  come  together  and 
form  large  drops  which  are  too  heavy  to  remain  in  the  air. 
Rain  then  takes  place,  and  continues  if  the  condensation  con- 
tinues. The  study  of  the  causes  which  produce  rain  is  one  in 
which  the  United  States  Government  is  much  interested,  and 
for  which  large  sums  of  money  are  spent  annually.  Thanks 
to  these  investigations,  which  are  country-wide,  we  are  able 
to  state  definitely  just  what  the  conditions  are  preceding  a 
rainstorm. 

In  the  prevailing  westerlies  there  are  vast  whirlpools,  just 
as  there  may  be  in  flowing  water.  Underneath  one  of  these 
whirlpools  there  is  less  air  pressing  upon  the  earth  than  there 
is  anywhere  near  the  whirlpool.  We  call  this  section  a  "  low  " 
because  a  barometer,  which  indicates  the  pressure  of  the  air, 
would  show  a  low  pressure.  Just  as  in  a  whirlpool  in  water 
the  neighboring  water  rushes  in  to  fill  up  the  whirlpool,  so  the 
air  rushes  from  all  directions,  over  a  space  of  thousands  of 
square  miles,  towards  the  center  of  one  of  these  lows.  If  a 
low  passes  to  the  north  of  us,  the  wind  will  come  from  the 
south  to  fill  it  up.  This  south  wind,  on  account  of  its  warmth, 
contains  a  great  deal  of  water  vapor.  As  it  travels  north  it 
becomes  colder,  about  one  degree  Fahrenheit  for  each  geo- 
graphical degree,  roughly,  sixty-eight  miles.  The  air  also 
rises  as  it  comes  north,  and  becomes  cooler,  one  and  six 
tenths  degrees  Fahrenheit  for  every  three  hundred  feet  which 
it  ascends.  Both  these  conditions  rapidly  lower  the  temper- 
ature of  the  whole  mass,  and  the  point  at  which  the  air 
can  no  longer  hold  water  vapor  is  rapidly  reached.  This  is 
called  the  saturation  point,  and  at  this  point  fog  and  cloud 
are  produced.  Any  further  cooling  of  the  air  produces  rain. 
The  scientific  name  for  a  "  low  "  is  "  cyclone." 


146         INTRODUCTION  TO  GENERAL  SCIENCE 

References :  — 

1.  1103  : 142-145.  Rainfall  and  its  Causes. 

2.  1304 :  249-250.  Rain,  Snow,  Hail. 

3.  1304 :  262-266.  Storms  and  their  Causes. 

a.    1102 : 285-292.     Causes,  Measurement,   and  Distribution 

of  Rainfall. 
6.    1302  :  327-334.     Rainfall  and  its  Distribution. 

c.  1305  :  71-73.         Rain,  Snow,  Sleet. 

d.  1307  :  239-246.     Rain,  Rainfall,  Snow,  and  Hail. 

e.  1308:110-112.     Rainfall. 

/.  1309  :  249-253.  Causes  of  Rainfall. 

g.  1310:373.  Rain  Making. 

h.  1311:231-236.  Rainfall. 

i.  1312  :  386.  Cyclonic  Rains. 

./.  1313  : 190-191.  Causes  of  Rainfall. 

107.    WEATHER  OBSERVATIONS 

In  about  eighty  places  scattered  over  the  United  States, 
the  United  States  Government  takes  observations  of  the 
weather  every  morning  except  Sunday,  at  8  A.M.,  Washington, 
D.C.,  time.  These  records  are  then  compiled  at  various 
head  stations,  where  each  day  at  about  2  o'clock,  Washing- 
ton time,  a  map  is  published  which  shows  the  conditions  of 
the  weather  all  over  the  country.  These  maps  are  distributed 
freely  to  schools  and  to  other  public  institutions.  One  who 
will  study  such  a  map  will  obtain  a  great  deal  of  information 
concerning  the  weather,  and  if  a  series  of  maps  is  examined 
carefully,  not  merely  scanned,  nearly  every  change  known 
about  the  weather  will  be  manifest. 

References :  — 

1.  1103:274-292.  Weather  Maps  and  Weather  Predictions. 

2.  1304 :  426-427.  Weather  Maps. 

a.    1 102  :  318-333.     Weather  Observations  in  the  United  States. 
&.    1301 : 102-104.     Weather  Maps. 


WEATHER  OBSERVATIONS  147 

c.  1302  :  279.  Private  Weather  Observations. 

d.  1303  :  81-82.         Weather  Predictions. 

e.  1307  :  264-266.     Weather  Forecasting. 

/.    1309  :  237-238.  Weather  Forecasts  and  the  Weather  Maps. 

g.    1310 :  402-430.  Weather  Maps. 

h.    1311 :  246-247.  The  Mapping  of  Temperature. 

i.    1312:390-393.  Weather  Maps. 

3.  Weather  Bureau.  Explanation  of  the  Weather  Map. 
Reprints  from  Yearbook  of  Department  of  Agriculture. 

4.  1900.  Amplification  of  Weather  Forecasts. 

5.  1906.  New  Problems  of  the  Weather. 

6.  1907.  The    Weather    Bureau    and  the    Public 

Schools. 

Experiment  56.  —  Temperature  Curves. 

Apparatus :  Thermometer. 

Materials :  Cross-section  paper.  (Sections  about  J  inch 
square.) 

a.  Take  thermometer  home  and  record  readings  of  tem- 
perature every  hour  from  7  A.M.  to  8  P.M. 

6.  Place  the  cross-section  paper  with  the  long  side  next  to 
you  and  mark  off  the  hours  on  every  other  line  beginning 
with  6  A.M.  and  ending  with  9  P.M.  On  the  left  side  of  the 
paper  mark  off  the  temperatures,  beginning  at  a  temperature 
5°  below  the  lowest  reading  which  you  took.  Use  one  square 
for  each  degree.  On  the  7  A.M.  line  make  a  cross  opposite 
the  reading  for  that  time.  Use  the  same  method  for  successive 
hours.  Now  run  a  smooth  curve  through  all  of  the  crosses, 
and  the  temperature  curve  is  finished. 

c.  What  was  the  temperature  at  9.30  A.M.?  Obtain  the 
information  from  your  curve.  This  is  an  example  of  inter- 
polation. What  was  the  temperature  at  6  A.M.?  Extend 
the  curve  in  the  way  in  which  it  would  seem  to  go  naturally. 
This  is  an  example  of  exter potation. 


148          INTRODUCTION  TO  GENERAL  *  SCIENCE 

108.    WEATHER  AND  CLIMATE 

The  condition  of  the  atmosphere  for  any  particular  day  is 
the  weather  of  that  day.  The  average  of  the  weather  for  the 
whole  year  is  the  climate  of  a  particular  locality.  The  cli- 
matic conditions  are  the  sum  total  of  all  the  weather  condi- 
tions which  take  place  in  the  year,  and  govern,  to  a  great 
extent,  the  suitability  of  the  locality  for  agricultural  purposes 
or  a  place  of  residence.  Persons  do  not  realize  what  a  great 
influence  weather  has  upon  human  beings,  and  yet  the  studies 
of  the  United  States  Government  are  bringing  those  facts  very 
strongly  before  the  people  of  the  United  States  at  the  present 
time.  There  are  certain  localities  in  which  it  is  nothing  less 
than  suicide  for  some  persons  to  live,  and  there  are  other  lo- 
calities which  tend  to  develop  bad  traits  of  character  in  certain 
individuals,  because  of  the  continued  physical  discomfort  they 
produce. 

References:  — 

1.  1103:269-274.  Weather. 

2.  1103:293-312.  Climate  of  the  World. 

3.  1304 :  275-279.  Influences  which  Affect  Climate. 

4.  Bulletin  No.  311.  Weather  Bureau.     Climate. 

5.  Bulletin  No.  312.  Weather   Bureau.      Invariability    of   our 

Winter  Climate. 
Reprints  from  Yearbook  Department  of  Agriculture. 

6.  1906.     New  Problems  of  the  Weather. 

7.  1908.     The  So-called   Change    of    Climate  in  the    Semiarid 

West. 

a.    1101 :  85.  Weather  Defined. 

6.    1102:333-334.  Climate. 

c.  1302 :  335-348.  Weather  and  Climate. 

d.  1303:74-81.  Weather  Changes. 

e.  1303:82-85.  Climate. 


WEATHER  INSTRUMENTS  149 

/.    1305  :  292-295.  Weather  and  Climate. 

g.    1308 :  99-100.  Climate  and  Factors  of  Climate. 

h.    1309 :  210-217.  Weather  and  Climate. 

i.    1310:440-461.  Climate   and    the   Determination    of   its 

Zones. 

j.    1311 :  268-270.  Weather  and  Climate. 

k.   1312 :  388-390.  Weather  and  Climate. 

I.    1312  :  394-395.  Changes  in  Climate  Questioned. 

m.  1313  :  171-175.  Weather  and  Climate. 


109.    WEATHER  INSTRUMENTS 

It  is  desirable,  for  many  reasons,  to  measure  the  factors 
which  go  to  make  the  weather,  such  as  rainfall,  temperature, 
wind  velocity  and  direction,  humidity,  atmospheric  pressure, 
and  sunshine.  The  different  pieces  of  apparatus  used  for  this 
purpose  are  called  weather  instruments. 

The  rain  gauge  collects  the  water  which  falls  in  a  measured 
area,  and  the  thickness  of  the  layer  of  rain  which  fell  is  easily 
computed,  or  even  measured. 

Temperature  is  measured  by  a  metallic  thermometer  which 
records  its  readings  on  a  moving  cylinder  of  paper.  Its  name 
is  thermograph.  The  recording  barometer  makes  its  record 
in  much  the  same  way,  and  is  called  a  barograph. 

Wind  direction  is  indicated  by  a  weather  vane;  its  velocity 
by  revolving  hemispheres,  called  an  anemometer. 

Humidity  is  measured  by  the  dew-point  apparatus  or  by 
means  of  a  wet-bulb  thermometer.  The  drier  the  air,  the 
greater  the  evaporation  from  the  cloth  around  the  wet  bulb, 
and  therefore  the  temperature  of  the  bulb  is  reduced.  Tables 
of  relative  humidity  may  be  consulted  for  desired  answers. 

The  sunshine  recorder  absorbs  enough  heat  from  the  sun- 
shine to  close  an  electric  circuit  by  means  of  expanding  mer- 


150          INTRODUCTION  TO  GENERAL  SCIENCE 

cury.     The  duration  of  sunshine  may  then  be  recorded  eleo 
trically. 

References :  — 

1.  1103:104-105.          The  Anemometer. 

2.  1103  : 123-125.  The  Psychrometer  and  the  Hah*  Hygrom- 

eter. 

3.  1103  : 145.  The  Rain  Gauge. 

4.  1103  : 164.  The  Piche  Evaporimeter. 

5.  1304  :  420-425.  Meteorological  Instruments. 

6.  1803  : 102-103.  The  Wet-  and  Dry-bulb  Thermometer. 

7.  1803  : 136-137.          Maximum  and  Minimum  Thermometers. 

8.  Bulletin  No.   235 : 5-8.     Weather   Bureau.     The  Sling   Psy- 

chrometer and  the  Dew-point  Apparatus. 

9.  Bulletin  No.  285.      Weather  Bureau.     Measurement  of  Pre- 

cipitation. 

a.    1101 : 11—41.         Weather  Instruments. 
6.    1302  :  398-404.     Meteorological  Instruments. 

110.    HOME-MADE  WEATHER  INSTRUMENTS 

The  United  States  Department  of  Agriculture  in  its  Year- 
book for  1907  published  directions  for  constructing  home- 
made weather  instruments.  Reprints  may  be  obtained,  free 
of  charge. 

References :  — 

Reprint  from  Yearbook  Department  of  Agriculture. 
1.    1907.     The  Weather  Bureau  and  the  Public  Schools.     Pages 
272-274.     Home-made  Instruments. 

Pupils  should  be  encouraged  to  make  these  simple  instru- 
ments at  home  and  use  them. 

111.    THE  OCEAN 

The  ocean  occupies  about  three  fourths  of  the  surface  of 
the  earth,  varying  in  depth  from  a  few  feet  to  about  five 


THE  OCEAN  151 

miles.  It  is  an  interesting  fact  that  the  highest  mountain 
peak  is  about  five  miles  above  sea  level,  so  that  the  largest 
variation  in  the  surface  of  the  earth  is  about  ten  miles.  Water 
in  large  masses  affects  the  climate  of  a  locality  to  a  very 
marked  degree.  It  acts  as  a  sort  of  balance  wheel  to  the 
temperature,  retarding  its  rapid  rise  as  well  as  prolonging  the 
warmth  far  into  the  winter  time.  We  learned,  under  Con- 
vection of  Heat,  that  a  whole  mass  of  water  must  be  warmed 
before  we  can  raise  any  part  to  a  high  temperature.  We  also 
learned  that  it  takes  more  heat  to  warm  water  than  any  other 
substance,  and  that,  having  become  warm,  water  stays  warm 
longer  than  any  other  substance.  It  is  quite  probable  that  if 
it  were  not  for  the  ocean,  the  earth  would  become  unbearably 
hot,  and  also  it  is  quite  likely  that  during  the  cold  weather 
the  temperature  would  fall  far  below  that  at  which  life  can 
be  maintained. 

The  ocean  serves  as  a  pathway  for  trade,  and  a  country  is 
fortunate  which  has  a  long  coast  line  with  many  inclosed 
bays  and  harbors.  Transportation  by  ocean  is  necessarily 
cheaper  than  by  rail,  because  there  are  no  roadways  to  main- 
tain, and  in  the  case  of  sailing  vessels  there  is  no  expense  for 
power.  See  Section  202,  Nature  and  Business. 

On  account  of  the  mobility  of  water,  storms  at  sea  become 
much  more  dangerous  than  storms  on  land,  for  the  water  is 
picked  up,  forming  large  billows,  which,  by  reason  of  their 
mass,  may  overwhelm  and  destroy  the  vessels;  and  the  wind, 
having  an  unimpeded  pathway,  blows  much  more  fiercely  on 
the  open  ocean  than  on  the  land. 

The  ocean,  because  of  its  unlimited  supply  of  fish  of  all 
kinds,  is  a  never  failing  source  of  income  to  those  who  make 
fishing  their  business.  Thus  it  is  that  we  are  dependent  upon 
the  ocean  in  more  ways  than  are  at  first  manifest. 


152          INTRODUCTION  TO  GENERAL  SCIENCE 

References :  — 

1.  1103:296-299.  The  Effect  of  the  Ocean  on  Climate. 

2.  1304:277.  Influence  of  Water, 
a.   1302:244-249.  The  Oceans. 

6.    1303 :  96-98.  The  Forms  and  Exploration  of  the  Ocean. 

c.  1305:109-121.  The  Sea. 

d.  1309  : 192-199.  Ocean  Currents ;  their  Causes  and  Effects. 

e.  1310 :  492-495.  Composition  of  Sea  Water. 
/.    1311:279-290.  The  Ocean. 

g.    1312:169-196.  The  Ocean. 


112.    PURIFICATION  OF  WATER 

Water  is  purified  by  nature,  and  also  by  man,  who  employs 
the  same  methods.  In  fact,  it  should  be  clearly  comprehended 
that  man  can  make  use  only  of  natural  phenomena  in  any  of 
his  work.  All  he  can  do  is  to  control  these  phenomena  within 
certain  limits. 

Water  evaporates  from  the  surface  of  the  ocean,  or  other 
bodies  of  water,  and  from  the  land,  to  form  water  vapor,  which 
condenses  again  to  water.  Only  pure  water  evaporates. 
This  is  nature's  method  of  distillation.  Man  distills  water 
in  a  still.  See  Section  27,  Distillation  of  Liquids. 

Some  rocks  are  very  porous  and  allow  water  to  pass  through, 
but  prevent  solid  matter  from  passing.  Man  uses  a  filter 
composed  of  some  porous  material,  such  as  cotton,  charcoal, 
sand,  or  unglazed  clay.  The  latter  is  often  in  the  form  of  a 
cylinder,  the  filtered  water  passing  into  the  cylinder  and 
leaving  the  dirt  on  the  outside,  whence  it  can  be  easily  re- 
moved. This  is  the  Pasteur  filter. 

Some  chemicals  may  be  held  in  solution  and  cannot  be 
removed  by  a  filter.  See  Section  115,  Solution  and  its 
Effects.  Chemical  means  may  then  be  employed  instead  of 


PURIFICATION  OF   WATER  153 

distillation.  Usually  a  chemical  can  be  added  which  will  form 
an  insoluble  compound  with  the  chemical  which  the  water  con- 
tains. This  produces  a  precipitate  which  can  be  removed  by 
filtration,  or  by  sedimentation. 

Bacteria  and  sewage  may  be  removed  by  passing  air  into 
the  water  and  by  the  effects  of  sunlight.  Nature  effects  this 
result  in  waterfalls  and  rapids.  Water  frozen  just  at  the 
freezing  point  is  comparatively  pure.  Boiling  will  kill  the 
bacteria,  but  will  not  remove  the  poisons  which  the  bacteria 
have  produced. 

There  may  be  substances  in  water  which  have  a  lower 
boiling  point  than  water.  If  so,  they  must  be  distilled  off 
first,  and  thus  removed  before  the  water  itself  is  distilled. 
Finally,  there  may  be  poisons  in  the  water  which  cannot  be 
removed  by  any  feasible  means.  See  Section  196,  Water 
Analysis. 
References :  — 

1.  1501 : 137.  Purification  of  Water. 

2.  1702 :  64-65.  Methods  of  Improving  Drinking  Water. 

3.  1703  :  45-47.  Purification  of  Water. 

a.  1701 :  50-54.  Purification  of  Water. 

b.  1704  :  28-33.  Purification  of  Water. 

c.  1706  :  39-40.  Purification  of  Water. 

d.  1707  :  69.  Purification  of  Water. 

e.  1708 :  268-270.  Purification  of  Water. 

/.  1709  :  302-323.  Purification  of  Water  by  Chemical  Means. 

g.  1711 :  2-3.  Preparation  of  Pure  Water. 

h.  1801:281-282.  Distillation, 

i.  1804:287-288.  Distillation. 

j.  1808:234-235.  Distillation. 

Experiment  57.  —  Precipitation  and  Filtration. 
Apparatus :  Ring  stand,  burner,  asbestos  mat,  evaporating 
dish,  test  tubes  6"  X  j",  funnel,  filter  paper. 


154          INTRODUCTION  TO  GENERAL  SCIENCE 

Materials:  Hydrochloric  acid,  1-4;  common  salt,  silver 
nitrate  solution,  5  per  cent;  sulphuric  acid,  1-6;  copper  sul- 
phate solution,  10  per  cent;  barium  chloride  solution,  5  per 
cent;  ammonium  sulphide,  10  per  cent;  lead  nitrate  solution, 
5  per  cent. 

a.  Dissolve  some  salt  in  a  little  water  and  taste  it.  Filter 
and  taste.  Did  the  salt  pass  through  the  filter  paper  ?  Put 
the  salt  solution  in  the  evaporating  dish,  on  the  asbestos  mat, 
and  boil  slowly  to  dryness.  How  does  the  amount  of  salt 
compare  with  the  original  amount  ?  If  sand  and  sugar  became 
mixed,  how  could  you  separate  them? 

6.  Take  a  teaspoonful  of  silver  nitrate  solution  and  filter 
it.  Does  anything  remain  on  the  filter  paper?  Now  add 
a  few  drops  of  hydrochloric  acid,  and  filter.  The  acid  has 
changed  the  silver  nitrate,  which  is  soluble,  into  the  insoluble 
silver  chloride.  There  is  no  more  silver  in  the  solution. 
Repeat,  using  a  solution  of  salt  in  the  place  of  hydrochloric 
acid.  Silver  nitrate,  then,  is  a  test  for  a  chloride. 

c.  Try  the  effect  of  the  solution  of  barium  chloride  upon 
solutions  of  copper  sulphate,  and  sulphuric  acid.     Note  that 
the  addition  of  hydrochloric  acid  produces  no  effect.    If  barium 
chloride  produces  a  white  precipitate  in  any  liquid,  in  the 
presence  of  hydrochloric  acid,  it  indicates  that  there  was  a 
sulphate  present. 

d.  Try  the  effect  of  ammonium  sulphide  upon  a  solution 
of  lead  nitrate.     Try  the  effect  of  lead  nitrate  upon  a  solution 
of  ammonium  sulphide.     Each  is  a  test  for  the  other.     A 
solution  of  lead  nitrate  is  a  test  for  the  presence  of  any  sul- 
phide. 


SPRINGS  AND  STREAMS  155 


113.    SPRINGS  AND  STREAMS 

Streams  may  have  their  source  from  mere  surface  water 
which  collects  in  the  valleys,  or,  as  is  more  often  the  case, 
from  water  which  comes  from  beneath  the  earth  and  forms 
what  is  called  a  spring.  The  water  seems  to  come  upward, 
but  in  reality  it  is  actually  flowing  downward  from  some 
higher  place.  Springs,  as  a  rule,  contain  comparatively  pure 
water,  but  there  are  many  mineral  springs  which  are  used  for 
medicinal  purposes.  These  latter  contain  various  minerals 
dissolved  in  the  water,  and  are  often  very  powerful  in  their 
action  upon  the  human  system,  and  even  harmful,  if  taken  in 
excess. 

The  water  of  rivers  is  usually  not  as  pure,  for  surface  drain- 
age carries  much  foreign  matter  into  them,  and  a  river,  free 
from  waterfalls  and  rapids,  soon  becomes  contaminated  with 
all  sorts  of  refuse  matter,  and  even  disease  germs.  Very 
often  sewage  of  cities  empties  into  rivers,  rendering  them 
unfit  for  domestic  purposes,  unless  purified  by  some  of  the 
methods  given  in  the  preceding  section. 

References :  — 

1.  1205  :  41-42.  Wells  and  Spring  Water. 

2.  1304:50-51.  Rivers. 

3.  1601 : 179-180.  The  Effect  of  Atmospheric  Pressure  on 

Springs. 

4.  1702 :  59-64.  Mineral  Waters  and  Wells. 

5.  1703  :  43-45.  Natural  Water  and  its  Impurities. 

6.  1710 :  62.  River  and  Spring  Water. 

7.  1901 :  222-224.          Water  and  Disease. 

a.    1206 : 145-150.     Springs  and  Artesian  Wells. 

6.    1209  :  79-83.         Springs,  Mineral  and  Thermal,  and  Wells. 

c.    1305 : 195-201.     Springs  and  Artesian  Wells. 


156          INTRODUCTION  TO  GENERAL  SCIENCE 

d.  1305:205-206.     Streams. 

e.  1306 :  228-230.     Springs  and  Artesian  Wells. 
/.    1309 :  41-43.         Hot  Springs  and  Geysers. 

g.    1311 : 100-104.     Mineral  Springs,  Geysers,  and  Wells. 
h.    1312:51-52.         Spring  Deposits. 

i.    1902 : 135-136.     The  Contamination  and   Purification  of 
Streams. 

114.    COMPOSITION  OF  WATER 

For  a  long  time  water  was  considered  as  an  element  and  not 
a  compound  as  we  now  know  it  to  be.  In  Section  66,  Chem- 
ical Effects  of  Electricity,  we  learned  that  water  could  be 
separated  into  two  parts  of  hydrogen  and  one  part  of  oxygen, 
both  by  volume.  It  can  be  shown  that  the  same  proportion 
of  hydrogen  and  oxygen  may  be  mixed  and  exploded,  pro- 
ducing nothing  but  water.  Also,  hydrogen  may  be  burned 
quietly  with  the  same  result,  without  the  explosion.  See  Sec- 
tion 1,  Explosions. 

Hydrogen,  as  a  word,  means  "  water  producer."  It  is  very 
useful  for  obtaining  high  temperatures,  since  the  flame  of 
hydrogen,  burned  in  oxygen,  is  the  hottest  known  flame.  If 
such  a  flame  impinges  upon  a  stick  of  unslaked  lime,  the  lime- 
light, sometimes  called  the  calcium  light,  is  produced.  The 
light  nearly  all  comes  from  the  intensely  hot  piece  of  calcium 
oxide,  or  lime,  which  does  not  burn  or  fuse.  Hydrogen  is  the 
lightest  gas  and  is  used  to  fill  balloons  where  great  lifting 
power  is  desired. 

References :  — 

1.  1702 :  56-57.  Chemical  Composition  of  Water. 

2.  1703 :  38-39.  Nature  of  Water. 

a.  1701 :  40-42.  Composition  of  Water. 
6.  1704 :  24-26.  Composition  of  Water, 
c.  1706 :  50-58.  Composition  of  Water. 


COMPOSITION  OF   WATER  157 

d.  1707 :  59-65.         Composition  of  Water. 

e.  1708  :  266-267.     Water  and  Its  Composition. 
/.    1711 :  6-10.  Composition  of  Water. 

Experiment  58.  —  To  Prepare  Hydrogen. 

Apparatus :   Test  tube  8"  X  1",  rubber  stopper  with  two 
holes,  thistle  tube,  evaporating  dish,  ring  stand,  asbestos  mat, 
burner;  otherwise  the  same  apparatus  as  in  Experiment  3. 
•  Materials :   Granulated  zinc,  hydrochloric  acid,  1-4. 

a.  Put  a  few  pieces  of  zinc  in  the  test  tube  and  cover  them 
with  water.  Insert  the  stopper,  placing  the  thistle  tube  so 
that  it  reaches  below  the  surface  of  the  water  in  the  tube. 
The  delivery  tube  should  be  in  the  other  hole.  Fill  bottles  as 
in  the  Oxygen  experiment.  Add  acid  to  the  zinc  through  the 
thistle  tube,  and  collect  four  bottles  of  hydrogen.  Keep  the 
bottles  bottom  side  up;  otherwise  the  hydrogen  will  escape. 

6.  Light  the  hydrogen  in  one  bottle,  and  describe  its  com- 
bustion. Does  hydrogen  support  the  combustion  of  wood  ? 

c.  Place  the  mouth  of  a  bottle  filled  with  air  against  the 
mouth  of  a  bottle  filled  with  hydrogen,  and  invert  them  several 
times.     Bring  the  mouths  of  the  bottles  near  a  flame.     What 
happens  ?     Why  ?  i 

d.  Turn  a  bottle  of  hydrogen  right  side  up  and  try  to  light 
it  after  one  minute.     What  is  the  result?     Explain. 

e.  Boil  to  dryness  the  liquid  from  the  hydrogen  generator. 
It  is  zinc  chloride.     Expose  the  dried  salt  to  the  air,  and  tell 
what  happens. 

EXPERIMENT  FOR  THE  TEACHER 
The  Philosopher's  Lamp 

Use  a  generator  similar  to  the  above,  but  in  the  place  of  the 
delivery  tube  insert  a  tube  which  has  been  drawn  out  to  form 
a  fine  tip.  After  adding  the  acid,  collect  some  of  the  hydrogen 


158          INTRODUCTION  TO  GENERAL  SCIENCE 

in  an  inverted  test  tube.  If  this  explodes,  collect  successive 
tubes  until  the  hydrogen  so  collected  burns  quietly.  Then 
light  the  hydrogen  at  the  tip.  The  yellow  color  of  the  flame 
is  due  to  the  sodium  in  the  glass. 

Hold  beaker  of  water,  which  is  dry  on  the  outside,  but 
filled  with  cold  water,  in  the  flame,  and  notice  the  large 
amount  of  water  which  collects  from  the  combustion  of  the 
hydrogen.  This  also  proves  that  water  is  composed  of 
hydrogen  and  oxygen. 

115.    SOLUTION  AND  ITS  EFFECTS 

We  are  inclined  to  think  of  solution  as  the  disappearance  of 
a  solid  within  a  liquid.  While  this  kind  of  solution  is  most 
common,  it  is  better  to  look  upon  solution  as  the  uniform  mix- 
ture of  the  particles  of  one  substance  throughout  the  particles 
of  another  substance.  We  can  have  a  solution  of  a  gas  within 
a  gas,  called  diffusion;  of  a  gas  within  a  liquid,  called  absorp- 
tion; a  gas  within  a  solid,  called  occlusion;  of  a  liquid  within 
a  liquid,  called  diffusion;  of  a  liquid  within  a  solid,  called 
water  of  crystallization  ;  and  of  a  solid  within  a  solid,  called  alloy. 

If  a  solid  is  dissolved  in  a  liquid,  the  boiling  point  of  the 
liquid  is  raised,  while  the  freezing  point  is  lowered.  Thus  the 
addition  of  common  salt  to  water  enables  a  cook  to  boil  the 
food  at  a  slightly  higher  temperature,  which  may  be  desired 
in  some  cases.  Likewise,  the  addition  of  salt  to  ice  produces 
a  mixture  which  has  a  lower  temperature  than  the  ice  alone. 
The  salt  causes  the  ice  to  melt,  and  the  necessary  heat  is  taken 
from  the  solution.  The  latter  does  not  freeze  on  account  of 
the  salt. 

Platinum  absorbs  hydrogen  and  combines  it  with  oxygen 
at  its  surface  so  rapidly  that  the  heat  is  sufficient  to  raise 
the  hydrogen  to  its  kindling  temperature.  Automatic  gas 


SOLUTION  AND  ITS  EFFECTS  159 

lighters,  cigar  lighters,  and  the  burning  points  of  pyrographic 
instruments  receive  their  heat  from  thus  combining  hydro- 
gen, or  compounds  of  hydrogen,  by  platinum,  with  oxygen. 

A  solid  is  said  to  be  insoluble  when  less  than  one  part  is 
dissolved  in  1000  parts  of  the  solvent,  while  it  is  called  soluble 
if  one  part  can  be  dissolved  in  100  parts  of  the  solvent.  As  a 
rule,  solids  are  more  soluble  in  hot  than  in  cold  liquids.  The 
solution  of  solids  usually  lowers  the  temperature  of  the  solvent. 
References :  — 

1.  1501 :  22.  Water  and  Solution. 

2.  1703  :  58-63.  Solution  and  its  Effects. 

3.  1803  : 121-124.       Solution  and  Crystallization. 
a.    1607  :  38-39.     Solution  of  Solids. 

6.  1611 :  55-59.  Plant  Food  in  Soil  Water. 

c.  1701:94-99.  Solution. 

d.  1704:30-31.  Solution. 

e.  1706:41-48.  Solution. 

/.  1707 :  70-72.  Water  as  a  Solvent. 

g.  1709 :  40-45.  Water  and  Solution. 

h.  1711 : 12-20.  Solution. 

i.  1805:117.  Solution. 

j.  1807 : 191.  Heat  of  Solution  —  Freezing  Mixtures. 

k.  1808 :  29.  Solutions. 

Experiment  59.  —  Solution  and  its  Effects. 
Apparatus :  Ring  stand,  asbestos  mat,  -burner,  thermom- 
eter, beaker,  100  c.c.,  platinum  wire  No.  30,  5"  long,  forceps. 
Materials:  Common  salt,  ammonium  nitrate,  ice. 

a.  Warm  some  water  in  the  beaker.     Note  the  bubbles  of 
air  which  come  out  of  the  solution. 

b.  Boil  the  water,  and  obtain  its  temperature.     While  still 
heating  add  a  little  salt,  and  note  the  change  of  temperature. 
Continue   to  add  salt   until  the  maximum  temperature  is 
reached.     How  much  is  it  ? 


160          INTRODUCTION  TO  GENERAL  SCIENCE 

c.  Take  some  cold  water  and  add  ice  to  it.     What  is  its 
temperature  ?    Add  some  salt,  and  record  the  lowest  tempera- 
ture which  you  can  obtain. 

d.  Take  some  ice  water,  remove  the  ice,  and  add  some 
ammonium  nitrate.     What  was  the  lowest  temperature  which 
you  obtained  ? 

e.  Take  some  cracked  ice  and  add  ammonium  nitrate  to  it. 
What  was  the  lowest  temperature  obtainable? 

/.  If  there  is  gas  in  the  laboratory,  hold  the  platinum  wire 
coiled  into  a  small  spiral,  by  means  of  the  forceps,  in  the  gas 
flame.  Shut  off  the  gas  and  turn  it  on  again  with  the  plati- 
num still  in  the  gas.  The  gas  should  ignite. 

116.    USES  OF  WATER 

Water  is  used  for  drinking,  cleansing,  and  agriculture. 
Aside  from  drinking  purposes,  water  owes  its  usefulness  to  the 
fact  that  it  readily  dissolves  many  substances.  Thus  in 
cleansing,  water  and  soap  dissolve  the  dirt,  while  in  agricul- 
ture water  holds  in  solution  the  plant  food  which  comes  from 
the  soil.  See  Section  115,  Solution  and  its  Effects.  In 
Section  208,  Simple  Household  Remedies,  we  will  take  up  a 
consideration  of  drinking  water,  while  in  Section  196  we  will 
study  the  analysis  of  water.  Section  146  treats  of  the  im- 
portance of  water  in  agriculture. 

On  account  of  its  mobility  and  noncompressibility,  water  is 
useful  as  a  means  of  conveying  pressure  which  may  be  util- 
ized in  water  motors  and  hydraulic  elevators.  Waterfalls 
can  be  used  to  turn  wheels  and  produce  mechanical  energy, 
which  may  be  changed  into  electrical  energy  capable  of  being 
used  at  a  great  distance. 

Water  is  taken  as  the  standard  of  density,  and  the  density 


USES  OF   WATER  161 

of  any  material,  referred  to  water  as  a  standard,  is  called  its 
specific  gravity.  The  specific  gravity  of  any  material  may 
be  obtained  by  finding  the  buoyant  force  which  the  water 
exerts  upon  it,  when  it  is  entirely  submerged.  The  total 
weight  of  a  body,  divided  by  the  loss  of  weight  in  water,  gives 
the  specific  gravity  of  the  body.  The  specific  gravity  of  a 
liquid  may  be  learned  by  dividing  the  loss  of  weight  of  a  body 
of  known  weight,  when  immersed  in  a  given  liquid,  by  the 
loss  of  weight  of  the  same  body,  when  immersed  in  water. 

References :  — 

1.  1501:135-137.  Drinking  Water. 

2.  1503  :  19.  Water  in  Living  Things. 

3.  1601 :  155-156.  Amount  of  Water  Used  by  Crops. 

4.  1605  :  67.  Importance  of  Water. 

5.  1710:61-64.  Water. 

6.  1803  :  48-50.  The  Hydraulic  Elevator  and  City  Water 

Supply. 

7.  1803  :  51-52.  The  Principle  of  Archimedes. 

a.  1606 :  47-51.  Why  Moisture  is  Important. 

b.  1701 :  55.  Uses  of  Water. 

c.  1704 :  21-23.  Uses  of  Water. 

d.  1705:161-162.  Water. 

e.  1706 :  31-38.  Water  in  Nature. 

/.    1711 :  1-2.  Water  and  its  Occurrence. 

g.    1712 :  60-61.         Uses  of  Water. 

Experiment  60.  —  Specific  Gravity  —  Buoyancy. 

Apparatus :  Platform  balance  on  a  stand,  and  set  of  weights, 
battery  jar,  6"  X  8",  pieces  of  iron,  lead,  glass,  aluminum,  and 
blocks  of  wood. 

a.  Weigh  the  piece  of  iron  in  air,  and  then  weigh  it  while  it 
is  entirely  submerged  in  water.  Subtract  this  last  weight 
from  its  weight  in  air.  This  is  the  loss  of  weight  and  is  due 
to  the  buoyant  force  of  the  water,  and  is  equal  to  the  weight 


162          INTRODUCTION  TO  GENERAL  SCIENCE 

of  the  water  displaced.     To  obtain  the  specific  gravity  of  iron, 
divide  the  weight  in  air  by  the  loss  of  weight. 

b.  Repeat  the  above  method,  using  lead,  glass,  and  alumi- 
num. 

c.  Float  the  block  of  wood  and  estimate  how  much  of  it  is 
below  the  surface  of  the  water.     The  amount  below  water 
divided  by  the  whole  thickness  of  the  block  will  give  the 
specific  gravity  of  any  floating  body. 


117.    SURFACE  TENSION 

In  Section  39  we  learned  that  universal  gravitation  acts  not 
only  between  every  two  bodies,  but  also  between  every  two 
particles  of  any  one  body.  We  would  expect,  then,  that 
matter  would  contract  until  it  became  a  solid  mass  with  no 
space  between  the  molecules.  This  would  happen  if  it  were 
not  for  heat,  which  is  molecular  motion.  The  effect  of  con- 
traction, however,  is  visible  on  the  surface  of  liquids,  either 
in  films  or  in  drops.  The  manifestation  of  this  attraction 
is  called  surface  tension,  meaning  the  pulling  together  of  the 
surface. 

On  account  of  surface  tension  any  liquid  which  is  freed 
from  gravity,  or  is  moving  as  fast  as  gravity  can  make  it  move, 
assumes  the  spherical  form,  as  in  the  case  of  raindrops  or  shot. 
Shot  is  made  by  pouring  melted  lead  from  the  top  of  a  shot 
tower  and  receiving  the  lead  drops  in  water,  which  prevents 
deformation.  The  circle  is  the  figure  which  contains  the 
greatest  area  with  the  least  perimeter,  while  the  sphere  is  the 
solid  which  contains  the  greatest  amount  of  material  with 
the  least  surface.  For  that  reason  shot  and  raindrops  assume 
the  spherical  form  due  to  their  surface  tension.  Soap  bubbles 


SURFACE  TENSION  163 

tend  to  become  smaller,  if  left  on  the  pipe,  because  the  surface 
contracts  and  drives  out  the  contained  air. 

The  attraction  between  the  molecules  of  one  body  is  called 
cohesion;  that  between  the  molecules  of  different  bodies  is 
called  adhesion.  In  order  that  a  liquid  may  wet  another  body, 
adhesion  must  be  stronger  than  cohesion.  Bugs  and  water 
spiders  can  walk  on  water  because  the  force  of  cohesion  of  the 
water  molecules  is  greater  than  the  force  of  adhesion  between 
the  water  and  the  feet  of  the  spiders.  On  the  other  hand,  if 
water  wets  an  object,  it  produces  the  same  effect  as  a  very  weak 
glue;  that  is,  stickiness. 

Warming  a  liquid  increases  the  motion  of  the  molecules  and 
thereby  weakens  the  surface  tension.  Dissolved  substances 
also  weaken  surface  tension. 

References :  — 

1.  1601 :  72-73.  Surface  Tension  in  Soils. 

2.  1803:113-116.  Surface  Tension, 
a.    1607  :  36-37.  Surface  Tension. 
6.    1801 :  99-101.  Surface  Tension. 

c.  1802  :  26-28.         Surface  Tension. 

d.  1804  : 134-135.     Surface  Tension. 

e.  1805 : 121-122.     Surface  Tension. 

/.  1806:57-61.  Surface  Tension.     Oil  on  Water. 

g.  1807  :  151-153.  Surface  Tension. 

h.  1808:110-112.  Surface  Tension. 

i.  1809 :  99-100.  Surface  Tension. 

Experiment  61.  — Surface  Tension. 

Apparatus :  Glass  tumbler,  mosquito  netting  and  cardboard, 
each  4"  X  4",  medicine  dropper,  cake  pan  8"  X  12",  funnel. 

Materials:  Alcohol,  camphor,  small  chip  of  wood,  soap. 

a.  Fill  tumbler  full  of  water,  lay  the  piece  of  mosquito 
netting  on  top  of  the  water,  and  the  card  upon  the  mosquito 


164          INTRODUCTION  TO  GENERAL  SCIENCE 

netting.  Carefully  invert  and  remove  the  card.  The  water 
should  stay  in  the  glass.  Compare  Experiment  42.  Why 
does  not  the  water  come  through  the  holes  in  the  netting? 

6.  Hold  the  glass  over  the  sink,  and  with  a  curved  medicine 
dropper  place  a  few  drops  of  alcohol  on  the  netting.  Tell  and 
explain  what  happens. 

c.  Place  the  little  chip  of  wood  upon  the  water  in  the  cake 
pan  and  carefully  deposit  one  drop  of  alcohol  at  one  end  of  tjie 
chip.     Tell  and  explain  what  happens.     Fill  the  pan  with 
fresh  water,  wash  the  chip,  and  replace  it  on  the  water.     Then 
put  a  small  piece  of  camphor  at  one  end  of  the  chip  so  that 
the  camphor  is  in  contact  with  the  water.     Describe  and  ex- 
plain the  result. 

d.  Use  the  funnel  as  a  bubble  pipe,  and  blow  a  soap  bubble. 
Stop  blowing  and  watch  the  bubble.     Why  does  it  contract? 
When  it  becomes  straight  across  the  large  end  of  the  funnel, 
what  happens?     Explain. 

118.  CAPILLARITY 

Capillarity  consists  of  those  effects  of  surface  tension  which 
are  manifested  in  tubes.  If  one  end  of  a  tube  of  small  diam- 
eter, open  at  both  ends,  is  placed  in  water,  the  water  will 
rise  in  the  tube  above  the  surface  of  the  outside  water.  The 
reason  for  this  is  as  follows :  the  force  of  adhesion  between 
the  water  and  the  glass  is  stronger  than  the  force  of  cohesion 
between  the  water  molecules,  and  the  water  creeps  up  the  walls 
of  the  tube.  Immediately  the  surface  of  the  liquid  within  the 
tube  contracts,  on  account  of  surface  tension,  and  pulls  up 
the  rest  of  the  water  in  the  tube.  This  action  continues  unti1 
the  weight  of  the  water  in  the  tube  equals  the  force  of  adhesion. 
The  smaller  the  tube  is,  the  higher  the  water  rises. 

Examples  of  capillarity  are  everywhere  present.     Blotting 


CAPILLARITY  165 

paper,  mops,  and  lampwicks  are  common  instances,  while 
plants  and  the  soil  furnish  other  examples  which  may  be  less 
understood.  The  stalks  of  plants  are  composed  of  fine  tubes, 
while  the  texture  of  the  soil  is  such  that  there  are  countless 
microscopic  passages  in  it  through  which  water  can  pass. 
See  Section  164,  Plant  Stems,  and  Section  147,  How  Water 
is  Held  in  the  Soil. 

Some  chemical  substances  crystallize,  leaving  capillary 
passages  through  which  more  of  the  solution  may  pass.  The 
result  is  that  the  material  will  creep  out  of  the  dish  in  which  it 
has  been  placed.  Ammonium  chloride,  commonly  called  sal 
ammoniac,  is  the  best  example  of  a  creeping  salt. 

References :  — ' 

1.  1605  :  85.  Movement  of  Water  in  Soil. 

2.  1702 :  240-241.  Capillarity  in  Plants. 

3.  1803:116-121.  Capillarity. 

4.  Farmers'  Bulletin  No.  266:  7.     Movement  of  Water  in  Soils. 

5.  Farmers'  Bulletin  No.  408  :  40-41.     Capillarity, 
a.    1606 :  48.  Capillary  Water. 

6.  1607 : 161-174.  Capillary  Movements  of  Soil  Moisture. 

c.  1612:41.  Capillary  Water. 

d.  1801 :  101-103.  Capillary  Phenomena. 

e.  1802  :  28-30.  Capillary  Action. 
/.  1804:133-137.  Capillarity. 

g.  1805:123-124.  Capillarity. 

h.  1806 :  61-62.  Capillary  Action. 

i.  1807 :  153-155.  Capillarity. 

j.  1808:112-114.  Capillarity. 

Experiment  62.  —  Capillarity. 

Apparatus:  Beaker  250  c.c.,  two  beakers  100  c.c.,  several 
glass  tubes  of  different  internal  diameter,  lampwick,  crystal- 
lization dish  5"  diameter,  ring  stand,  asbestos  mat,  burner. 

Materials:  Ammonium  chloride. 


166          INTRODUCTION  TO  GENERAL  SCIENCE 

a.  Stick  several  of  the  capillary  tubes  into  water,  side  by 
side.     How  does  the  height  of  rise  of  water  compare  with  the 
diameters  ? 

b.  Take  two  tubes  of  the  same  internal  diameter,  and  place 
one  in  cold  water,  the  other  in  boiling  hot  water.     Carefully 
compare  the  heights  of  the  two  columns.     What  are  your 
conclusions  ? 

c.  Fill  the  large  beaker  with  water,  wet  a  lampwick  and 
bend  it  over  the  edge  of  the  beaker,  so  that  the  longer  end  is 
outside.     Place  the  beaker  in  the  crystallization  dish,  and 
leave  for  a  day.     Compare  the  results  with  those  of  Experi- 
ment 45.     Why  is  it  not  necessary  to  start  the  action  in  this 
experiment  ? 

d.  Make  a  saturated  solution  of  ammonium  chloride,  fill 
the  small  beaker  half  full,  and  set  away,  for  a  few  days.     De- 
scribe the  result. 

119.    OSMOSIS 

All  gases,  liquids,  and  solids  tend  to  diffuse,  and,  if  the  dif- 
fusion is  hindered,  a  pressure  proportional  to  the  diffusion 
tendency  is  produced.  If  two  liquids  are  separated  by  a 
membrane  which  hinders  the  passage  of  one  of  the  substances, 
a  difference  of  pressure  is  manifested.  The  process  is  called 
osmose,  and  the  pressure  is  called  osmotic  pressure. 

Osmose  takes  place  naturally  in  seeds  and  roots,  the  sur- 
faces of  which  allow  water  to  enter,  but  do  not  allow  the  ma- 
terial inside  to  pass  out.  Thus  the  beginning  and  the  growth 
of  plants  are  dependent  upon  osmose.  See  Section  163,  Plant 
Roots,  and  Section  168,  Fruits  and  Seeds.  The  swelling  of 
beans,  when  "  put  to  soak  "  is  due  to  osmose,  or,  as  it  is  more 
often  called,  osmosis. 

Pieces  of  bladder,  or  any  animal  tissue,  such  as  gold  beater's 


OSMOSIS  167 

skin  and  skin  of  an  egg,  also  show  this  same  effect.  In  addi- 
tion to  the  vegetable  and  animal  membranes,  there  is  one 
chehiical  membrane  which  is  especially  useful  for  showing 
osmotic  pressure.  This  is  formed  by  the  combination  of 
copper  sulphate  and  potassium  ferrocyanide  to  produce 
copper  ferrocyanide.  If  this  compound  is  formed  within  the 
pores  of  an  unglazed  earthenware  cup,  a  strong  semipermeable 
cell  is  obtained. 

References :  — - 

1.  1407 :  36-39.  Osmosis  in  Plants. 

2.  1503 :  78.  Expansive  Force  of  Germinating  Seeds. 

3.  1601 : 147-153.  Osmosis  and  Diffusion  in  Plant  Feeding. 

4.  1605:65-66.  Osmosis. 

5.  1702  :  241-242.  Osmosis  in  Plants. 

6.  1703  : 132-133.  Osmotic  Pressure. 

V.   Farmers'    Bulletin  No.    408 :  13-15.     How     Roots    Absorb 

Moisture. 

a.    1607:41-48.  Osmosis. 

&.    1611 :  2-4.  The  Way  the  Seed  Gets  Water  from  the  Soil. 

c.  1612  :  47-48.  Roots  Take  Nourishment  by  Osmosis. 

d.  1707  :  447-448.  Osmotic  Pressure. 

e.  1801 :  20.  Osmosis. 
/.    1805:117-118.  Osmosis. 
g.    1808:116.  Osmose. 

h.    1809 :  92.  Osmose  of  Gases. 

Experiment  63.  —  Osmotic  Pressure. 

Apparatus:  Bottle,  6  oz.,  with  stopper,  string,  porous  cup 
4"  X  2",  stopper  to  fit,  with  one  hole,  glass  tube  -§•"  diameter, 
4'  long,  battery  jar  6"X8". 

Materials :  Beans,  copper  sulphate,  potassium  ferrocyanide, 
sugar. 

a.  Fill  the  bottle  with  beans,  and  then  fill  the  spaces  with 
water.  Stopper  the  bottle  tightly,  and  tie  in  the  stopper.  It 


168         INTRODUCTION  TO   GENERAL  SCIENCE 

may  be  well  to  wrap  the  bottle  with  string.  Leave  until  next 
day,  and  explain  the  result. 

6.  It  is  advisable  to  make  all  of  the  osmotic  pressure  cells 
at  one  time,  or  the  teacher  may  make  only  one  and  show  its 
action  to  the  class. 

Make  a  saturated  solution  of  copper  sulphate  and  a  satu- 
rated solution  of  potassium  ferrocyanide  solution.  Fill  the 
porous  cup  with  the  potassium  ferrocyanide  solution,  wait 
five  minutes,  and  then  place  the  porous  cup  in  the  copper  sul- 
phate solution.  The  two  solutions  will  then  meet  somewhere 
within  the  walls  of  the  porous  cup.  Leave  for  half  an  hour. 
Save  the  solutions. 

Fill  the  osmotic  cell  (porous  cup)  with  a  saturated  solution 
of  sugar,  insert  the  long  tube  in  the  stopper,  and  push  the 
stopper  firmly  into  the  porous  cup  so  that  the  solution  runs  a 
few  inches  up  the  tube.  Now  set  the  osmotic  cell  in  the  bat- 
tery jar  and  fill  the  jar  until  the  water  stands  at  the  same 
level  as  the  sugar  solution  in  the  tube.  If  the  osmotic  cell  is 
good,  the  solution  will  rise  in  the  tube.  If  it  does  not  do  so, 
remake  the  cell. 

120.    REMOVAL  OF  GREASE  SPOTS  AND  STAINS 

For  the  removal  of  stains  we  have  at  our  command  three 
methods:  solution,  capillarity,  and  chemical  action.  The 
method  to  be  employed  must  be  determined  by  its  effect  on 
the  material  which  is  being  cleaned.  For  that  reason  the  use 
of  chemical  action  is  somewhat  limited,  while  some  solvents 
affect  dyes. 

To  remove  grease  by  solution,  use  ammonia  water,  gasoline, 
naphtha,  benzine,  alcohol,  or  ether.  Ether  is  the  most  expen- 
sive, but  it  can  dissolve  some  substances  better  than  any  other 
solvent. 


REMOVAL  OF  GREASE  SPOTS  AND  STAINS  169 

To  remove  grease  by  capillarity,  place  a  cloth  or  blotting 
paper  under  the  goods,  cover  the  goods  with  paper,  and  press 
with  a  moderately  hot  flatiron.  Heat  weakens  surface  ten- 
sion, and  the  grease,  after  melting,  moves  away  from  the  iron. 

Pitch,  gums,  shellac,  rubber,  and  cement  may  be  dissolved 
by  the  same  solvents,  except  ammonia  water,  as  were  used  in 
the  removal  of  grease.  Carbon  bisulphide  is  most  useful  for 
rubber.  To  remove  pitch  or  other  sticky  gums  from  the 
hands,  use  kerosene. 

Ink  spots  should  have  salt  put  on  them  at  once.  Then 
they  may  possibly  be  removed  by  warm  water.  If  this  has  no 
effect,  use  lemon  juice,  and  finally  a  10  per  cent  oxalic  acid 
solution.  This  is  a  poison.  Remove  the  oxalic  acid  by  wash- 
ing immediately  in  water.  Red  ink  may  be  removed  by 
ammonia  water  or  ether. 

Plaster  can  be  removed  from  floors  and  baseboards  by  means 
of  hydrochloric  acid,  10  per  cent  solution. 

Paint  may  be  removed  by  turpentine  or  benzine. 

Iron  rust  may  be  dissolved  by  a  5  per  cent  solution  of  hy- 
drochloric acid.  Dip  the  spot  into  a  shallow  dish,  containing 
the  acid,  and  then  pour  on  some  ammonia  water  to  stop  the 
action  of  the  acid.  Delicate  fabrics  will  not  stand  this  treat- 
ment. Lemon  juice  and  salt  should  be  applied,  in  this  case, 
and  the  article  be  placed  in  the  sunshine.  * 

Reference :  — 

1.    1710:93-96.     Cleansing. 

Experiment  64.  —  The  Removal  of  Stains. 

Apparatus:  Beakers,  evaporating  dishes. 

Materials :  Pieces  of  cloth,  4"  X  4",  any  grease,  ink,  paint, 
pitch,  gasoline,  benzine,  kerosene,  turpentine,  alcohol,  ammo- 
nia water,  oxalic  acid,  10  per  cent,  hydrochloric  acid,  5  per 
cent. 


170         INTRODUCTION  TO  GENERAL  SCIENCE 

a.  Put  some  grease  on  four  pieces  of  the  cloth  and  try  to 
remove  it  by  gasoline,   benzine,   turpentine,  and  ammonia 
water.     Arrange  the  solvents  in  the  order  of  their  rapidity  of 
action. 

b.  Put  some  black  and  red  ink  spots  on  one  cloth,  and  allow 
it  to  dry.     Repeat  with  a  second  cloth,  but  try  oxalic  acid 
at  once,  on  the  black  spot,  and  ammonia,  or  ether,  on  the  red 
spot.     After  the  first  becomes  dry,  try  to  remove  the  spots  by 
the  same  method.     Should  spots  be  removed  at  once? 

c.  Put  paint  on  a  cloth  and  allow  it  to  dry.     Put  some  more 
paint  on  another  cloth  and  try  to  remove  it,  at  once,  with 
turpentine  or  benzine.     Next  day  try  to  remove  the  dried 
paint.     Conclusions  ? 

d.  Put  some  iron  rust  on  a  piece  of  cloth  and  try  to  remove 
it  with  the  5  per  cent  solution  of  hydrochloric  acid.     Do  not 
remove  the  hydrochloric  acid  from  the  cloth,  and  note  how 
rotten  the  cloth  becomes  after  a  week's  time. 

121.    ACIDS,  BASES,  AND  SALTS  —  NEUTRALIZATION 

Science  classifies  matter  according  to  its  known  effect  upon 
certain  other  kinds  of  matter.  One  of  these  test  substances 
is  litmus,  a  vegetable  product.  Certain  materials  cause  blue 
litmus  to  turn  red;  we  call  them  acids:  others  cause  red  lit- 
mus to  turn  blue;  those  are  named  bases.  When  litmus  turns 
red,  we  call  it  an  acid  reaction;  if  it  turns  blue,  we  call  it  an 
alkaline  reaction.  Phenolphthalein  is  another  test.  Acids 
have  no  effect  on  it,  but  bases  turn  it  red,  after  which  acids 
will  remove  the  color. 

Acids  all  contain  hydrogen,  which  may  be  set  free  from 
some  acids  by  means  of  metals.  See  Section  114,  Composi- 
tion of  Water.  Bases  all  contain  at  least  one  part  of  hydro- 


ACIDS,  BASES,  AND  SALTS  171 

gen  and  one  part  of  oxygen.  If  an  acid  is  mixed  with  a  base, 
the  hydrogen  of  the  acid  and  the  combination  of  hydrogen 
and  the  oxygen  of  the  base  combine  to  form  water.  The 
result  is  that  both  the  acid  and  the  base  lose  their  character- 
istics, and  a  salt  is  formed.  This  can  be  obtained  by  boiling 
away  the  water.  A  salt,  then,  is  the  result  of  the  combina- 
tion of  part  of  an  acid  with  part  of  a  base,  water  being  formed 
at  the  same  time.  We  call  this  action  neutralization.  Most 
salts  do  not  affect  litmus  paper  or  phenolphthalein;  that  is, 
they  are  neutral. 

Sometimes  there  is  an  excess  of  acid  in  a  person's  stomach, 
which  may  be  shown  by  testing  the  saliva  with  litmus  paper. 
Ordinary  baking  soda  will  neutralize  the  acid  and  "  sweeten  " 
the  stomach.  See  Section  208,  Simple  Household  Remedies. 

Sour  milk  contains  an  acid  which  can  be  neutralized  by 
baking  soda.  Carbon  dioxide  is  set  free  from  the  baking  soda 
as  fast  as  neutralization  takes  place.  Cream  of  tartar  has 
acid  characteristics,  and  for  that  reason  is  used  with  baking 
soda  to  set  free  the  carbon  dioxide.  The  bubbles  of  this  gas 
cause  the  dough  to  rise. 

The  soil  tends  to  become  slightly  acid  on  account  of  the 
excretions  from  the  roots  of  plants.  This  acidity  may  be 
corrected  by  the  application  of  lime.  See  Section  158,  The 
Liming  of  the  Soil. 

References :  — 

1.  1503  :  93.  Acid  Reaction  of  Root  Hairs. 

2.  1702  :  72-77.  Acids,  Bases,  Salts,  and  Neutralization. 

3.  1703  :  95-98.  Acids,  Bases,  Salts  —  Neutralization. 

a.  1701 :  106-109.  Acids,  Bases,  and  Salts  —  Neutralization 

6.  1704 :  58.  Acids,  Bases,  and  Salts. 

c.  1705:28-29.  Neutralization. 

d.  1706 :  87-98.  Acids,  Bases,  and  Salts. 


172          INTRODUCTION  TO  GENERAL  SCIENCE 

e.  1707 : 126-127.  Acids,  Bases,  Neutralization,  and  Salts. 

/.  1708  : 136-141.  Acids,  Bases,  and  Salts. 

g.  1709 :  116-120.  The  Action  of  Acids  and  Bases. 

h.  1711 : 125-127.  Acids,  Bases,  and  Salts. 

i.  1512  :  51-59.  Acids,  Bases,  and  Salts. 

j.  1713  : 100-101.  The  New  Theory  of  Acids. 

Experiment  65.  —  Acids,  Bases,  and  Salts  —  Neutraliza- 
tion. 

Apparatus :  Ring  stand,  asbestos  mat,  burner,  evaporating 
dish,  stirring  rod. 

Materials :  Sulphuric  acid,  nitric  acid,  hydrochloric  acid, 
all  1-4,  ammonium  hydrate,  sodium  hydrate,  potassium  hy- 
drate, sodium  carbonate,  sodium  bicarbonate,  hydrogen  potas- 
sium tartrate  (cream  of  tartar),  all  10  per  cent  solutions,  blue 
and  red  litmus  paper,  phenolphthalein  solution. 

a.  Test  with  blue  and  red  litmus  paper  the  effect  of  all  the 
materials,  using  the  stirring  rod  to  obtain  a  drop  of  each. 
Rinse  the  stirring  rod  in  water  after  each  test  before  making 
another  test.  Make  a  list  of  your  results  in  two  columns; 
call  one  red  or  acid,  the  other  blue  or  alkaline. 

6.  Fill  the  evaporating  dish  one  third  full  of  sodium  hydrate, 
and  add  a  few  drops  of  phenolphthalein.  What  color  does  it 
become  ?  Put  a  piece  of  blue  litmus  paper  and  a  piece  of  red 
litmus  paper  on  the  edge  of  the  dish  so  that  they  touch  the 
liquid.  Add  hydrochloric  acid  slowly  until  there  is  no  effect 
on  the  red  or  blue  litmus  paper.  If  too  much  acid  is  added, 
add  a  little  more  sodium  hydrate  until  there  is  neutralization. 
Then  boil  to  dryness.  Taste  of  the  result.  Do  you  recognize 
the  taste  ?  What  is  it  ? 

c.  Ask  your  teacher  for  a  few  pieces  of  litmus  paper  to  take 
home.  Test  sour  milk,  add  baking  soda,  and  test  again. 
Conclusions  ?  Test  vinegar,  washing  soda,  and  soaps. 


HYDROSCOPIC   AND  EFFLORESCENT  SALTS      173 


122.    HYGROSCOPIC  AND  EFFLORESCENT  SALTS 

When  salts  are  crystallized  out  of  a  water  solution,  they 
contain  a  certain  amount  of  water,  by  virtue  of  which  they 
are  able  to  take  the  crystalline  shape.  This  is  called  the 
water  of  crystallization,  and  is  a  fixed  amount  for  a  given  sub- 
stance. The  water  of  crystallization  may  be  driven  out  by 
heat,  sometimes  quietly,  and  sometimes  with  tiny  explosions 
caused  by  the  expansion  of  the  water  when  it  turns  to  steam. 
The  color  of  the  crystal  is  lost  and  it  becomes  white,  showing 
that  the  color  is  due  to  the  arrangement  of  the  molecules, 
rather  than  to  any  inherent  characteristics.  If  a  crystal  loses 
its  water  of  crystallization,  when  exposed  to  air,  it  is  said  to  be 
efflorescent. 

On  the  other  hand,  some  substances  attract  the  moisture  of 
the  air  and  form  chemical  compounds  with  it.  These  are 
called  hygroscopic  salts,  and  they  may  or  may  not  be  dry  after 
the  absorption  of  the  water.  If  they  become  wet,  they  are 
called  deliquescent.  Ordinary  lime,  unslaked,  is  an  example 
of  a  hygroscopic  substance  which  remains  dry,  although  ab- 
sorbing a  considerable  quantity  of  water.  Calcium  chloride 
and  zinc  chloride  are  examples  of  deliquescent  substances. 
See  Experiment  58. 

Since  the  absorption  of  the  water  vapor  of  the  air  is  the 
opposite  to  evaporation,  a  little  calcium  chloride  placed  in 
the  water  of  fire  pails  will  prevent  the  water  from  evapo- 
rating. 

Salts,  when  deprived  of  their  water  of  crystallization,  have 
no  fixed  shape  and  are  called  amorphous.  Some  amorphous 
salts  are  very  hygroscopic.  Molasses  is  an  example  of  an 
organic  compound  which  is  quite  hygroscopic. 


174         INTRODUCTION  TO  GENERAL  SCIENCE 

References :  — 

1.  1601 :  252.  Hydroscopic  Moisture. 

2.  1703:53-54.  Water  of    Crystallization  and   Mechani- 

cally Inclosed  Water. 

3.  1703  :  55-56.  Efflorescence,  Deliquescence,  etc. 
a.    1701 :  54-55.         Water  of  Crystallization. 

6.    1706 :  46-47.         Efflorescence  and  Deliquescence. 

c.  1707:56-57.         Water   of    Crystallization,    Efflorescence, 

and  Deliquescence. 

d.  1708 :  154-155.     Crystallization,    Efflorescence,  and   Deli- 

quescence. 

e.  1709  :  47.  Efflorescence  and  Deliquescence. 

/.    1712:67-68.         Water   of    Crystallization,    Efflorescence, 
and  Deliquescence. 

Experiment  66.  —  Efflorescence  and  Deliquescence. 
Apparatus :  Balance,  set  of  weights,  watch  glasses. 
Materials :    Sodium   carbonate   crystals,  sodium   sulphate 
crystals,  granulated  calcium  chloride,  sodium  hydrate  (solid). 

a.  Weigh  about  5  g.  of  sodium  carbonate  crystals  on  a 
watch  glass,  and  expose  to  the  air  for  twenty-four  hours. 
Then   weigh   again.     Do   the   same  with   sodium   suphate. 
Describe  the  results,  and  state  your  conclusions. 

b.  Perform  a  similar  experiment  with  calcium  chloride  and 
sodium  hydrate. 

123.    SOAP 

Soap  is  made  by  the  combination  of  organic  acids  with 
sodium  hydrate  (caustic  soda)  or  potassium  hydrate  (caustic 
potash).  The  process  of  soap  making  may  be  considered  as 
the  neutralization  of  the  hydroxide  by  the  acid  contained  in 
the  oil  or  grease.  Glycerine  is  formed  at  the  same  time,  and 
is  usually  saved.  Sodium  hydrate  produces  a  hard  soap, 
while  potassium  hydrate  is  used  to  manufacture  soft  soap. 


SOAP  175 

The  kind  of  soap  produced  depends  upon  the  materials  used 
and  the  care  with  which  the  soap  is  made.  Good  results  can 
be  obtained  only  from  good  material,  and  then  only  if  care  is 
exercised.  When  the  hydroxide  is  completely  "  saponified" 
there  is  no  free  alkali  and  the  soap  is  suitable  for  toilet  pur- 
poses. 

Cheap  soaps  are  usually  the  most  expensive,  as  the  free 
alkali  which  they  contain  will  destroy  fabrics  washed  with 
them. 

References :  — 

1.  1702:200-201.  Saponification. 

2.  1703:340-341.  Soap. 

3.  1710 :  96-103.  Soap  and  Soap  Powders. 

a.  1701 :  410-411.  Saponification. 

b.  1704 :  226-230.  The  Manufacture  of  Soap. 

c.  1705  :  156.  Saponification. 

d.  1706:422^23.  Soap. 

e.  1707 :  465-467.  Soap  and  its  Action  on  Hard  Water. 
/.  1708  :  206-207.  Soaps  and  their  Action. 

g.  1709  :  387-389.  Soap  and  Soap  Making. 

h.  1711 :  299-300.  Oils  and  Fats  —  Soap. 

i.  1712 :  300-302.  Soaps  and  their  Action. 

j.  1713  : 19.  Soaps,  Medicaments,  etc. 

Experiment  67.  —  To  Make  Soap. 

Apparatus:  Ring  stand,  burner,  iron  dish. 

Materials :   Lard,  sodium  hydrate,  15  per  cent  solution,  salt. 

a.  Take  about  60  c.c.  of  the  sodium  hydrate  solution,  in  the 
iron  dish,  and  add  about  25  g.  of  lard.  Boil  slowly  for  ten 
minutes,  and  then  add,  gradually,  about  15  g.  of  salt.  Con- 
tinue to  boil  for  a  few  minutes.  Allow  the  whole  to  cool,  and 
remove  the  soap,  which  will  be  on  top  of  the  mass.  Let  the 
cake  dry  for  a  few  days,  and  then  test  its  ability  to  produce 
suds. 


176         INTRODUCTION  TO  GENERAL  SCIENCE 

b.  Test  your  soap  with  litmus.     Do  you  think  that  your 
soap  would  make  a  good  toilet  soap? 

c.  Soft  soap  may  be  made  by  using  potassium  hydrate  and 
no  salt.     There  is  a  great  excess  of  the  alkali  in  soft  soap. 

124.    HARD  WATER 

Water  is  called  hard  or  soft  according  to  the  ease  with  which 
soap  forms  suds  in  it.  If  water  is  rendered  soft  by  boiling,  it 
is  called  temporarily  hard,  and  the  hardness  was  due  to  calcium 
carbonate,  which  was  dissolved  in  it.  This  calcium  carbon- 
ate, or  lime,  is  deposited  on  the  bottom  and  sides  of  the  tea- 
kettle. If  tested  with  hydrochloric  acid,  it  shows  itself  to  be 
a  carbonate.  See  Section  90,  The  Chemical  Engine. 

On  the  other  hand,  if  the  water  is  not  changed  by  boiling,  it 
is  called  permanently  hard.  In  this  case  calcium  sulphate  or 
magnesium  sulphate  is  present;  both  may  be  present.  Per- 
manently hard  water  can  be  rendered  soft  only  by  chemical 
means.  Boiling  alone  has  no  effect  on  it.  By  the  addition  of 
soaps,  chemical  compounds  are  formed  with  the  calcium  sul- 
phate, or  magnesium  sulphate,  which  are  insoluble,  and 
collect  as  a  scum  which  may  be  removed.  The  softened 
water  is  not  fit  to  drink,  but  is  excellent  for  cleansing  pur- 
poses. It  must  be  remembered,  however,  that  it  is  costly 
to  use  hard  water,  since  the  soap  used  to  soften  it  is  wasted 
as  far  as  the  real  cleansing  is  concerned.  For  the  testing  of 
water,  see  Section  196,  Water  Analysis. 

References :  — 

1.  1703 :  47.  Hard  and  Soft  Water. 

2.  1710:67-68.  Hard  Water. 

a.   1701 : 309-310.     Temporary  and  Permanent  Hardness  of 
Water. 


THE  EARTH'S  CRUST  177 

6.    1705:56-57.        Hard  and  Soft  Water. 

c.  1706 : 327.  Calcium   Compounds    and   Hardness    of 

Water. 

d.  1707  : 359-361.     Temporary  and  Permanent  Hardness. 

e.  1708:268.  Hard  Water. 
/.     1709:247-248.    Hard  Waters. 

g.    1712 :  65-67.        Soft  and  Hard  Waters. 

Experiment  68.  —  Temporary  Hardness. 

Apparatus:  Kipp  generator,  test  tube,  test-tube  holder, 
burner. 

Materials:  Marble  in  lumps,  hydrochloric  acid,  calcium 
hydrate  (limewater). 

a.  Fill  a  test  tube  half  full  of  limewater,  and  pass  carbon 
dioxide,  from  the  Kipp  generator,  into  it  slowly.  Tell  what 
happens.  Continue  to  pass  in  the  carbon  dioxide,  and  tell  what 
happens. 

6.  Warm  the  contents  of  the  test  tube,  and  tell  what  hap- 
pens. The  heat  causes  the  excess  of  carbon  dioxide  to  pass 
off,  and  the  calcium  carbonate  is  no  longer  soluble.  Thus 
heating  water  which  is  temporarily  hard  causes  the  dissolved 
material  to  be  precipitated. 

125.    THE  EARTH'S  CRUST 

We  see  agents  of  disintegration  acting  on  .the  earth's  surface, 
and  by  working  backward  we  shall  always  be  led  to  the  reali- 
zation that  once  all  must  have  been  solid  rock,  without 
any  covering  of  soil.  By  analyzing  soil,  we  find  that  it  is 
merely  changed  rock,  altered  both  physically  and  chemically, 
but  containing  the  material  which  goes  to  make  up  the  rock. 
Review  Section  30,  Chemical  and  Physical  Changes. 

Gradually  the  surface  became  covered  with  a  thin  soil 
which  slowly  grew  thicker  as  the  agents  of  erosion  continued 


178         INTRODUCTION  TO  GENERAL  SCIENCE 

to  act.  It  must  be  remembered,  however,  that  the  thickness 
of  the  earth's  crust  is  slight  compared  with  its  diameter,  and 
that  the  interior  of  the  earth  is  hot,  and  would,  under  ordinary 
conditions,  exist  in  a  liquid  form,  but  does  not  at  present,  on 
account  of  the  tremendous  pressure  which  it  bears.  In  deep 
mines  the  temperature  is  so  high  that  it  is  impossible  to  work 
continuously  more  than  a  short  time.  See  Section  48,  The 
Heat  of  the  Earth. 

References :  — 

1.  1205 : 17-21.  Mantle  Rock  and  the  Soil. 

2.  1304  : 16-22.  The  Solid  Earth. 

a.  1201 :  19-22.  How  the  Rocky  Crust  was  Hidden. 

6.  1203  : 13-19.  The  Decay  of  Rocks  and  the  Causes. 

c.  1209  :  16-17.  Weathering. 

d.  1302  :  29-31.  The  Earth  Crust ;  Mantle-Rock. 

e.  1303 : 134-138.  Activities  and  the  Wasting  of  the  Land. 
/.  1305 : 180-182.  The  Structure  of  the  Earth. 

g.    1309  :  75-76.         Relief  of  the  Land. 
h.    1311 :  11-13.         Continuous  Change. 

126.    CHANGES  IN  THE  SURFACE  OF  THE  EARTH 

By  "  changes  "  is  meant  all  those  modifications  of  the  sur- 
face which  have  taken  place  since  the  earth  became  cold 
enough  to  allow  water  to  fall  upon  it,  as  well  as  the  modifica- 
tions which  are  taking  place  at  the  present  time.  The  large 
changes,  such  as  the  formation  of  rocks,  and  the  building  of 
mountains,  will  be  taken  up  under  those  headings.  Now  we 
are  to  consider  those  alterations,  or  modifications,  which  affect 
and  have  affected  the  surface  itself;  by  "  surface  "  is  meant 
only  the  few  upper  feet  of  the  earth.  Refer  to  Section  139,  How 
Mountains  are  Made,  and  to  Section  133-137,  which  treat  of 
rocks  and  their  formation. 


WEATHERING  AND  RATE  OF  WEATHERING  179 

References :  — 

1.  1304:18-19.  Air,  Water,  Rock. 

2.  1601 :  27-28.  The  Origin  of  Soil. 

a.  1202 :  150-154.  Principles  Involved  in  Rock  Weathering. 

b.  1208  :  10-23.  Erosion  by  Air  and  Water. 

c.  1302  :  29-32.  The  Earth  Crust. 

d.  1307  :  24-25.  The  Rock  Mantle  and  its  Movements. 

e.  1608 :  24-28.  The  Source  and  Production  of  Soil. 
/.    1612  :  1-4.  The  Earth's  Clothing. 


127.    WEATHERING  AND  THE  RATE  OF  WEATHERING 

The  changes  which  occur  in  the  earth's  crust,  whether  they 
be  those  of  erosion  or  chemical  changes,  are  all  classified  under 
one  heading,  Weathering.  The  earth  is  very  different  from 
what  it  was  when  it  first  cooled  off,  both  in  shape  and  in  its 
surface  features,  as  well  as  the  character,  or  make-up,  of  its 
surface.  We  may  classify  these  under  Changes  in  the  Surface 
of  the  Earth,  Section  126,  but  for  purposes  of  study  they  are 
taken  separately.  See  Section  129,  Erosion. 

When  it  first  began  to  rain,  that  is,  when  water  could  exist, 
even  in  the  atmosphere  of  the  earth,  as  a  liquid,  the  enormous 
rainfall  accomplished  an  erosion  of  the  rocks  which  is  in- 
credible when  we  think  of  the  effects  of  a  modern  rainstorm. 
Then,  also,  as  the  water  wore  off  the  surface  of  the  earth,  the 
material  worn  off  formed  a  sort  of  protective  covering,  and 
thus  the  rate  of  weathering  became  less  as  time  went  on. 
Nevertheless,  water  still  continues  to  produce  more  rapid 
results  than  any  other  single  agent  of  weathering. 

References :  — 

1.  1205:5-38.  The  Work  of  the  Weather. 

2.  1304:38-40.  Weathering. 

3.  1304 :  41-42.  Rate  of  Weathering. 


180         INTRODUCTION  TO  GENERAL  SCIENCE 

4.  1601 :  9-15.  The  Atmosphere  and  its  Work. 

5.  1601 :  21-26.  Over  and  Over  Again. 
a.    1202  :  255-266.     Rate  of  Weathering. 

fr.  1203  :  13-19.  The  Decay  of  Rocks  and  the  Causes. 

c.  1206 :  124-127.  Difference  in  the  Rate  of  Weathering. 

d.  1209  :  16-17.  Various  Rates  of  Weathering. 

e.  1301 :  254-257.  The  Effects  of  Weathering. 
/.  1302  :  210-224.  Land  Sculpture. 

g.    1303  :  136-139.     The  Wasting  of  the  Lands. 
h.    1307:111.  Weathering  Processes. 

128.    AGENTS  OF  WEATHERING 

Without  doubt,  rain  produces  the  greatest  visible  change 
upon  rocks  and  the  soil,  yet  probably  the  action  due  to  the  air 
and  to  certain  microbes  accomplishes  an  amount  not  fully 
realized.  The  agents  of  weathering,  then,  are  rain,  and,  in 
fact,  water  in  all  its  forms,  —  for  large  masses  of  snow  and 
ice  accomplish  work  not  possible  to  water  alone,  —  heat  and 
cold,  the  oxygen  of  the  air,  and  various  microorganisms,  as 
well  as  some  plants  and  trees. 

We  learned  when  we  were  studying  heat  that  it  causes  the 
expansion  of  all  material,  and  the  expansion  is  pretty  nearly 
proportional  to  the  temperature.  Where  the  sun  shines  on 
exposed  rocks,  their  surface  becomes  hot  much  faster  than 
their  interior.  This  causes  their  surface  to  expand  faster 
than  their  interior,  making  the  outside  of  the  rock  too  large  to 
fit  on  the  inside,  so  that  there  is  a  separation  of  a  thin  layer. 
When  the  rock  becomes  cool  at  night,  the  reverse  action 
takes  place.  The  outside  contracts  more  rapidly  than  the 
inside,  since  radiation  takes  place  from  the  surface.  Then  the 
outside  is  too  small  for  the  inside,  and  peels  off.  We  call  this 
exfoliation,  and  if  we  are  on  the  watch,  we  may  see  many 
evidences  of  this  action. 


AGENTS  OF   WEATHERING  181 

Extreme  cold,  where  there  is  water  present,  is  one  of  the 
greatest  forces  in  weathering.  When  water  freezes,  it  expands 
about  one  eleventh  of  its  volume.  Water  is  everywhere  pres- 
ent in  crevices  and  even  within  many  rocks.  Therefore, 
whenever  cold  weather  comes,  this  water  freezes,  expands,  and 
breaks  the  rock  into  countless  numbers  of  pieces,  for  the  ex- 
pansive power  of  freezing  water  is  almost  irresistible.  When 
warmer  weather  comes,  the  ice  melts,  runs  out,  carrying  with  it 
the  smaller  pieces  of  rock  and  leaving  larger  gaps  behind  for 
rain,  the  roots  of  trees,  and  burrowing  animals,  to  enter. 
Water  pipes,  in  cold  places,  are  burst  in  a  similar  fashion. 

Chemical  changes  are  those  which  alter  the  make-up  of 
matter  in  its  finest  divisions.  On  the  surface  of  the  earth 
oxygen  is  the  most  active  in  producing  these  chemical  changes. 
Oxygen  combines  very  readily  with  a  large  number  of  ele- 
ments which  compose  the  surface  of  the  earth,  and  by  its  com- 
bination changes  insoluble  parts  into  other  substances,  which 
are  readily  soluble  in  water.  Thus  oxygen  prepares  the  way 
for  the  action  of  the  water,  which  is  twofold:  mere  wearing 
away,  and  solution.  Oxygen  is  especially  active  on  iron  com- 
pounds. 

In  organic  compounds,  that  is,  different  compounds  of 
carbon  which  have  had  life  at  some  time,  oxygen  produces  a 
decay,  or  aids  in  the  decay  started  by  certain  bacteria  which 
form  various  compounds  with  carbon  and  hydrogen.  There- 
fore oxygen,  working  in  conjunction  with  bacteria,  tends  to 
remove  all  dead  vegetable  and  animal  matter,  and  return  its 
constituents  either  to  the  ground  or  to  the  atmosphere.  Con- 
sequently the  same  material  is  used  over  and  over  again,  in 
plant  life  and  animal  life. 


182 


INTRODUCTION  TO  GENERAL  SCIENCE 


References :  — 

1.  1205:13. 

2.  1205:13-15. 

3.  1304:13-14. 

4.  1304:44-45. 

5.  1601:15-18. 

6.  1601 :  18-21. 

a.  1201:119-121. 

6.  1202 :  177-180. 

c.  1203:14-17. 

d.  1206:112-114. 

e.  1208:30-40. 
/.  1209 :  18-28. 
g.  1302:57. 

h.  1310:40-44. 

i.  1311 :  131-132. 

j.  1312 : 262. 

k.  1604:18-28. 

I.  1612:7-16. 


Oxidation. 

Effects  of  Heat  and  Cold. 

The  Atmosphere  in  Relation  to  Decay. 

Agents  of  Erosion. 

Water  and  its  Work. 

Living  Forms  and  their  Work. 

Work  of  Oxygen. 

Action  of  Freezing  Water  and  Ice. 

The  Causes  of  Decay  in  Rocks. 

The  Effect  of  Heat  and  Cold. 

Igneous  Agencies. 

Agents  of  Weathering. 

Weathering  by  Oxygen. 

Freezing  and  Thawing. 

The  Glacier's  Work, 

Disintegration  of  Rock  through  Heat. 

Effects  of  Weather  upon  the  Land. 

Soil  Makers. 


129.    EROSION 


Erosion  is,  as  has  been  stated,  the  most  rapid  factor  in 
weathering,  but  it  would  not  be  so  active  if  it  were  not  for  the 
work  of  the  other  factors.  The  work  of  running  water,  how- 
ever, is  very  great.  Deep  valleys  and  canons  have  been 
dug  by  moderate-sized  streams,  working  during  countless 
centuries;  in  other  valleys  lakes  have  been  formed  by  some 
stoppage  at  the  mouth  of  the  river.  The  result  of  the  water's 
work  has  been  to  carve  our  hills  into  their  present  state,  for  a 
large  number  of  our  mountains  were  really  huge  billows  in  the 
surface  of  the  earth,  until  water  cut  some  places  deeper  than 
others  and  gave  us  the  rugged,  cragged  mountains. 


AGENTS  OF  EROSION 


183 


References :  — 

1.  1205:56-60. 

2.  1304:51-54. 

3.  1304:66-68. 

4.  1601 :  15-18. 

a.    1201:23-26. 

6.  1203:108-110. 

c.  1301:257-260. 

d.  1302:57-67. 

e.  1303:245-249. 
/.  1303:256-261. 
g.  1305:181. 

h.    1309:75. 
i.    1310:86-91. 


Transportation  and  Erosion  by  Streams. 

The  Load  of  Rivers. 

Alluvial  Fans  and  Filling  of  Valleys. 

The  Work  of  Water. 

How  Erosion  Exposes  the  Rocks  to  our 

View. 

Rivers  and  the  Making  of  New  Land. 
Erosion  of  the  Land. 
Erosion. 
Work  of  Rivers. 
Development  of  Valleys. 
Weathering  and  Erosion  Defined. 
Erosion  Defined. 
Erosion  and  its  Effects. 


130.    AGENTS  OF  EROSION 

Next  to  rain  and  rivers,  the  wind  and  the  ocean  waves  are 
the  most  important  agents  of  erosion.  When  the  air  moves 
with  a  certain  rapidity,  it  picks  up  sand  and  small  pebbles 
and  hurls  them  against  rocks  and  mountains,  wearing  them 
away.  We  may  consider  that  the  wind  actually  becomes  a 
sand  blast,  each  particle  of  sand  and  pebble  becoming  a  sort  of 
chisel,  which  cuts  off  a  grain  here  and  a  grain  there  from  the 
mountain  side;  but  owing  to  the  countless  number  of  grains 
of  sand,  the  work  accomplished  is  sometimes  very  great.  In 
sandy  districts,  telegraph  poles  and  fence  posts  have  been  cut 
through  by  the  action  of  the  blowing  sand. 

There  is  another  form  of  water  erosion  besides  those  men- 
tioned which  has  a  limited  zone  in  which  to  work.  This  is  the 
wear  of  the  waves  upon  the  beaches  and  cliffs  which  form  the 
shore  of  the  ocean.  We  have  records  in  some  instances  where 
waves  have  removed  large  areas  of  land.  On  the  other  hand, 


184 


INTRODUCTION  TO  GENERAL  SCIENCE 


under  proper  conditions,  the  waves  pile  up  deposits  and  pro- 
duce new  land.  The  waves  work  their  way  through  rocks, 
forming  caves  and  caverns.  The  water  wears  away  the  softer 
parts  of  the  rocks,  and  does  not  affect  the  harder  parts  as 
much. 


Wind  Erosion. 

Sea  Erosion. 

Wind  Work  on  Deserts. 

Wave  and  Tide  Work. 

Action  of  W.'nd. 

Wind  Erosion. 

Force  and  Work  of  Waves. 

Wind  Erosion. 

Wave  Action. 

Wind  Action  in  Deserts. 

Work  of  the  Sea  on  the  Shore. 

Ocean  Erosion. 

Surface  Effect  of  Winds. 

The  Work  of  the  Wind. 

Erosion  by  Waves. 

Shore  Erosion. 


References  :  — 
1.    1205:144-153. 
2.    1205  :  156-161. 
3.    1304:87-88. 

4.    1304:210-215 

a. 

1202 

:  280-286. 

6. 

1206 

:  129-138. 

c. 

1209 

:  182. 

d. 

1211 

:  109-118. 

e. 

1302 

:  229-232. 

f. 

1303 

:  286-288. 

9> 

1303 

:  305-307. 

h. 

1306 

:  244-245. 

i. 

1309 

:  227-228. 

J- 

1310 

:  27-28. 

k. 

1310 

:  227-231. 

I. 

1312 

:  198-203. 

131.    DISINTEGRATION   DUE   TO    PLANT   AND   ANIMAL  LIFE 
—  BACTERIA 

We  are  continually  learning  more  about  the  effect  of  bac- 
teria on  all  the  changes  which  take  place  in  matter.  We  know 
that  they  play  a  great  part  in  the  disintegration  of  rock  and 
soil  material,  forming  plant  food  in  which  vegetables  may  have 
their  life.  Bacteria  aid  in  many  chemical  changes,  especially 
those  of  decomposition,  and  probably  aid  in  chemical  reactions 
to  a  considerable  extent.  Later  we  will  take  up  the  study  of 
bacteria  under  various  headings. 


SLOWNESS  OF  CHANGE  185 

Animals,  in  burrowing,  leave  holes  through  which  tree  roots 
may  easily  find  their  way  when  seeking  water.  These  holes 
also  allow  water  to  enter,  so  that  it  may  dissolve  the  lower 
soil  material  and  later  bring  it  to  the  surface. 

The  roots  of  plants  penetrate  far  into  the  soil,  and  by  their 
growth  lift  up  large  masses  of  ground.  They  even  penetrate 
minute  crevices  in  rocks,  and,  as  they  grow,  actually  split 
them  apart,  exposing  more  and  more  surface  of  the  rocks  to 
the  action  of  the  other  agents  of  weathering. 

References :  — 

1.  1205  :  20-21.  How  Humus  and  Subsoil  are  Mingled. 

2.  1304 :  40-41.  Organisms  as  Agents  of  Weathering. 

3.  1601 :  18-21.  Living  Organisms  and  their  Work, 
a.    1206 : 116-117.  Work  of  Burrowing  Animals. 

6.  1207 :  317-320.  The  Work  of  Burrowing  Animals. 

c.  1208  :  23-30.  Organic  Agents  of  Changes. 

d.  1302 :  59.  Plant  and  Animal  Disintegration. 

e.  1311 :  83-85.  Effect  of  Animals  on  Soil. 

/.  1312 :  262.  Disintegration  of  Rocks  by  Plants. 

g.  1508 :  153-154.  The  Usefulness  of  the  Earthworm. 

h.  1604 :  60-89.  Field  Laborers. 

i.  1612 : 17-22.  The  Soils  that  Living  Things  have  Made. 


132.    SLOWNESS  OF  CHANGE 

When  we  consider  the  action  of  the  various  factors  which 
have  changed  the  surface  of  the  earth,  we  must  not  lose  sight 
of  the  vast,  almost  incalculable,  period  of  time  through  which 
they  have  acted.  Rocks  have  been  formed  through  sedimen- 
tation, and  have  been  pushed  up  by  the  contraction  of  the 
earth's  surface.  They  have  then  been  worn  down  by  rain  and 
running  water,  and  have  formed  sand,  which  has  passed  to 
the  ocean,  to  enter  once  more  into  the  formation  of  rock.  In 


186         INTRODUCTION  TO  GENERAL  SCIENCE 

turn  these  rocks  have  been  raised  above  the  surface  of  the 
ocean  to  form  new  land.  Plants  have  lived,  borne  fruit,  died, 
decayed,  become  soil  again,  as  food  for  other  plants;  animals 
have  eaten  of  plant  food  and  died  and  fertilized  the  ground 
for  coming  generations  of  plants.  It  is  this  continual  change, 
which,  acting  through  a  length  of  time  that  is  almost  im- 
possible for  the  human  brain  to  conceive,  has  produced  our 
present  earth. 

References :  — 

1.  1205  :  5.  Slowness  of  Change. 

2.  1304 :  42-44.  Results  of  Weathering. 

3.  1304 :  45-46.  Age  of  the  Earth. 

4.  1601 :  21-26.  Over  and  Over  Again. 

a.    1207  :  343-348.     Results  of  Slowness  of  Change  as  Applied 

to  Agriculture. 
6.    1301 :  255.  Slowness  of  Change. 

c.  1312  :  270-273.     The  Geographic  Cycle. 

d.  1612 :  7-8.  Slowness  of  Change. 

133.    ROCKS  DEFINED  AND  CLASSIFIED 

We  call  the  material  of  which  the  earth  is  made,  rock,  and 
we  may  consider  that  the  whole  earth  is  made  of  rock.  This 
rock  has  been  changed  through  several  kinds  of  processes  into 
a  large  variety  of  sands,  clays,  and  soils.  The  kinds  of  rocks 
which  compose  the  surface  of  the  earth  are  divided  into  sev- 
eral classes,  according  to  the  way  in  which  they  were  formed. 
They  are:  sedimentary,  chemically  formed,  organic,  igneous, 
metamorphic,  and  seolian.  In  addition,  there  are  various 
combinations  of  these  rocks  which  cannot  be  classified. 

On  the  surface  of  the  earth  rocks  occur  which  are  called 
mantle  rock  on  account  of  being  loose,  and  forming  a 
mantle  over  the  surface  of  the  earth,  while  underneath  is  the 


DIFFERENCE  BETWEEN  MINERALS  AND  ROCKS  187 


solid  rock  which  constitutes  the  main  part  of  the  crust  of  the 
earth.  This  is  called  bed  rock.  Rock  may  be  carried  by 
streams  and  deposited  in  other  places,  where  it  has  not  previ- 
ously formed  a  part  of  the  earth,  and  this  is  called  transported 
rock. 


References :  — 

1.  1205:22-28. 

2.  1304:32-33. 

3.  1601:38-43. 

a.  1201:9-12. 

6.  1201:47-51. 

c.  1202 :  1-3. 

d.  1203:20-35. 

e.  1206:54. 

/.  1208:68-71. 

g.  1209:4-11. 

h.  1305:216-219. 

i.  1307:27. 

j.  1308:36-37. 

k.  1312:264-266. 


Movements  of  the  Mantle  of  Rock  Waste. 
Rocks  of  the  Earth's  Crust. 
Influence  of  Rock  Structure  in  Soil  For- 
mation. 

What  the  Earth  is  Made  Of. 
How  Rocks  are  Made. 
Definition  and  Occurrence  of  Rocks. 
How  Common  Rocks  are  Made. 
The  Formation  of  Rocks. 
Classification  of  Rocks. 
Transportation  and  Deposition  by  Wind. 
Transportation  of  Rock  by  Running  Water. 
Rock  and  its  Structure. 
Kinds  of  Rocks. 
Mantle  Rock. 


134.    THE  DIFFERENCE  BETWEEN  MINERALS  AND  ROCKS 

A  rock  is  a  combination  of  several  minerals,  usually  less 
than  four,  and  is  a  part  of  the  earth's  crust.  A  mineral  is  a 
definite  chemical  compound,  existing  in  rock  masses,  or  alone. 
Those  minerals  from  which  a  desired  element  may  be  obtained 
easily  are  called  ores. 


References :  — 

1.  1205:286-290. 

2.  1304:406-408. 

3.  1703:334. 

a.    1201:107-109. 


Mineral  Veins. 

Common  Minerals. 

Minerals  and  Ores  Defined. 

Difference  between  Rocks  and  Minerals. 


188  INTRODUCTION  TO  GENERAL  SCIENCE 

b.  1202  :  1-3.  Definition  of  Rocks. 

c.  1202  :  9-12.  The  Minerals  Constituting  Rocks. 

d.  1206 :  33-34.         Minerals  Have  a  Definite  Chemical  Com- 

position. 

e.  1208 :  36-37.         Rock,  a  Mixture  of  Minerals. 
/.  1209  :  192-193.     Properties  of  Minerals. 

g.  1210:233-234.     Mineral  Veins. 

h.  1301 :  221-225.     Minerals  of  the  Crust. 

i.  1305  :  180-181.     Minerals  and  Rocks. 

j.  1312 : 239-246.     Minerals. 


135.    ROCKS  OF  THE  EARTH'S  CRUST 

Sedimentary  Rocks.  —  The  rain  washes  pebbles,  sand,  and 
pieces  of  rock  down  from  the  hills;  these  are  carried  by  rivers 
into  lakes  and  the  ocean,  where  they  settle,  forming  layers 
along  the  bottom.  The  next  time  there  is  a  heavy  rush  of 
water  there  will  be  another  layer  formed,  and  thus  the  ma- 
terial is  built  up,  layer  upon  layer,  until  great  depths  have 
been  filled.  These  layers  are  called  strata,  and  the  rock  is  said 
to  be  stratified.  The  thickness  of  the  strata  depends  upon  the 
amount  of  material  which  was  brought  down  at  one  time. 
These  strata  are  naturally  horizontal  where  they  have  not 
been  disturbed.  We  will  study  the  result  of  their  disturbance 
under  the  formation  of  mountains.  As  time  goes  on,  the 
great  pressure  and  the  action  of  cementing  material  contained 
in  some  of  the  rocks  cause  these  rock  strata  to  become  solidi- 
fied into  one  huge  rock  mass,  maintaining,  however,  the  defi- 
nite strata  which  went  to  make  it. 

Igneous  Rocks.  —  Melted  rock  which  has  come  up  from 
within  the  earth  may  appear  either  on  the  surface,  or  may  fill 
crevices  and  caverns  below  the  surface.  When  cool,  it  is  called 
igneous  rock,  receiving  its  name  from  the  fact  that  it  was  once 


ROCKS  OF  THE  EARTH'S  CRUST  189 

very  hot.  If  the  cooling  has  taken  place  slowly,  we  have  a  crys- 
talline structure,  of  which  granite  is  an  example.  Where  the 
cooling  took  place  very  rapidly,  the  same  material  produced 
what  is  called  natural  glass,  or  obsidian,  having  no  structure 
whatever.  Where  lava  is  blown  up  by  the  expansion  of 
steam,  pumice  and  volcanic  ash  are  formed. 

Metamorphic  Rocks. — Where  rocks  have  been  subjected 
to  the  action  of  earth  heat,  or  great  pressure,  or  both,  certain 
changes  have  taken  place  in  them.  We  call  this  metamor- 
phism.  Thus  sandstones  may  become  a  solid  mass  of  quartz, 
and  shale  change  to  slate.  Coal,  in  some  cases,  has  been 
changed  to  graphite,  which  is  pure  carbon.  Under  the  effects 
of  metamorphism,  some  minerals  have  been  recrystallized, 
according  to  some  other  plan,  and  other  rocks  have  had  their 
nature  entirely  altered. 

Chemically  Formed  Rocks.  —  Nearly  all  of  this  kind  of 
rock  is  formed  beneath  the  surface  of  the  earth,  although  it 
does  appear  around  geysers  and  hot  springs.  Some  of  the 
minerals  through  which  water  flows  dissolve  when  the  water 
is  hot,  and  may  impart  carbon  dioxide  to  the  stream.  As  the 
water  cools  or  loses  its  carbon  dioxide,  the  dissolved  material 
is  deposited.  This  forms  stalactites  in  caverns,  calcareous 
tufa  around  the  hot  springs,  and  silica  around  the  geysers  of 
Yellowstone  Park. 

JEolian  Rocks.  —  There^  is  one  other  class  of  rocks  which, 
because  they  have  been  caused  by  winds,  are  called  ceolian. 
The  wind,  picking  up  sand  and  pebbles,  has  blown  them  into 
hollows,  and  as  the  centuries  went  by  has  piled  tons  upon  tons, 
which,  on  account  of  the  pressure,  and  the  presence  of  some 
cementing  material,  have  finally  formed  solid  rocks.  Sand 
dunes  may  be  considered  under  this  head,  although  they  are 
not  compact. 


190 


INTRODUCTION  TO  GENERAL  SCIENCE 


References :  — 

1.  1205:147-151. 

2.  1205:180-186. 

3.  1205:265-276. 

4.  1205:281-283. 

5.  1304:409. 

6.  1304:411-412. 

7.  1304 : 413. 

8.  1601:68-69. 

a.  1201:53-55. 

b.  1202:55-61. 

c.  1202:112-113. 

d.  1202 :  133. 

e.  1206:70-73. 
/.  1206:98-104. 

g.  1301:226-232. 

h.  1302:29-32. 

i.  1306:238-239. 

j.  1307:29-32. 

k.  1312:226-228. 


Wind  Deposits. 

Stratification  and  the  Rate  of  Deposi- 
tion. 

Underground  Structure  of  Igneous  Origin. 

Metamorphic  Rocks. 

Sedimentary  Rocks. 

Igneous  Rocks. 

Metamorphic  Rocks. 

Wind-formed  Soils. 

Three  Kinds  of  Sedimentary  Rocks. 

Igneous  Rocks. 

Sedimentary  Deposits. 

^Eolian  Rocks. 

Sedimentary  or  Stratified  Rocks. 

Metamorphic  Rocks  and  the  Result  of 
Metamorphism. 

Rocks  of  the  Earth's  Crust. 

Mantle  Rock  and  Bed  Rock. 

Wind  Erosion. 

Sedimentary  Rocks. 

Sand  Dunes. 


Experiment  69.  —  Sedimentation. 

Apparatus:  Student  lamp  chimney  with  stoppers  to  fit 
both  ends. 

Materials:    Coarse  gravel,  sand,  loam,  and  clay. 

a.  Mix  equal  parts  of  the  materials  to  make  enough  to  fill 
the  chimney  two  thirds  full.  Fill  rest  of  the  space  with  water. 
Then  stopper  and  shake  vigorously.  Allow  the  chimney  to 
stand  in  an  upright  position  until  the  water  becomes  clear. 
Describe  the  arrangement  of  the  materials.  Stratified  rock 
was  formed  by  the  transportation  of  different  materials  in 
water,  and  the  sedimentation,  while  slower,  was  similar  to 
that  which  took  place  in  the  lamp  chimney. 


ORGANIC  ROCKS  191 


136.    ORGANIC  ROCKS 

Wherever  the  word  organic  is  used,  it  is  to  be  understood 
that  the  material  which  "  organic  "  describes  once  possessed 
life,  either  vegetable  or  animal.  Many  animals  and  shellfish 
get  their  supply  for  shells  from  the  carbonate  of  lime  which  is 
dissolved  in  the  water.  When  these  animals  die,  their  shells 
become  compacted  by  pressure  of  one  layer  upon  the  other, 
and  form  limestone.  Another  factor  which  enters  into  the 
formation  of  rock  is  the  diatoms,  a  very  small  plant  which 
lives  at  the  surface  of  the  sea  in  warm  climates,  and  has  a 
shell-like  covering  containing  silica.  Large  masses  of  the  dead 
bodies  of  these  settle  to  the  bottom,  likewise  forming  rock, 
which  is  called  diatomaceous. 

Coral  islands  are  produced  by  the  gradual  accumulation  of 
coral  growth.  Coral  is  an  animal,  growing  in  a  shell,  and  the 
remains  which  we  see  are  merely  calcium  carbonate  with  a  few 
other  compounds  in  very  small  amounts.  An  acid  applied 
to  coral,  as  well  as  to  all  of  the  organic  rocks,  except  those  con- 
taining silica,  sets  free  carbon  dioxide. 

Diatomaceous  rock  is  used  for  polishing  purposes,  since  the 
little  particles,  although  very  fine,  are  sharp,  and  cut  away  the 
dirt  or  tarnished  material.  It  is  also  used  as  a  sound  proofing 
for  deadening  sound  in  buildings,  and  as  a  packing  for  fire 
proofing  and  for  cold-storage  plants.  Since  it  is  a  very  poor 
conductor  of  heat,  it  is  valuable  for  these  latter  purposes. 

References :  — 

1.  1304:410-411.  Organic  Rocks. 

2.  1503  :  202.  Coral  Reefs. 

3.  1703:200-201.  Natural  Carbonates. 
a.   1201 :  85-86.  Diatomaceous  Earth. 


192  INTRODUCTION  TO  GENERAL  SCIENCE 

b.  1201 :  87-91.  Limestone  and  Marble. 

c.  1202  :  123-128.  Diatomaceous  Earth  and  the  Carbonates. 

d.  1206  :  89-96.  Organic  Rocks. 

e.  1208 :  28-30.  Formation   of   Limestone,   Diatomaceous 

Earth,   etc. 

/.    1209  : 175-183.     Geological  Work  of  Marine  Animals. 
g.    1311:76.  Limestone. 

h.    1312  :  258.  Calcareous  and  Carbonaceous  Rocks. 

Experiment   70.  —  To   Test   Rocks. 
Apparatus :  Medicine  dropper. 

Materials:  Marble,  coral,  limestone,  unknown  rocks,  soil, 
hydrochloric  acid,  10  per  cent. 

a.  Using  the  medicine  dropper,  put  a  drop  of  acid  upon 
each  of  the  known  rocks  and  note  the  bubbling  or  effervescence 
which  indicates  the  liberation  of  carbon  dioxide. 

b.  Test  the  unknown  rocks  and  the  samples  of  soil.     You 
can  recognize  the  carbonates  by  this  method. 

Imitation  coral  is  a  porcelain  and  cannot  be  detected  by 
sight  or  feeling.  A  drop  of  hydrochloric  acid  proves  the  true 
coral  if  bubbles  of  a  gas  are  produced. 

137.    COAL,  SOFT  AND  HARD 

Another  variety  of  organic  rock  is  coal.  In  prehistoric 
times  plants  grew  to  an  enormous  size,  so  that  the  remains 
accumulated  very  fast,  and  there  was  a  thick  layer  of  decayed 
vegetable  matter  on  the  ground.  On  account  of  the  great 
amount  of  rain,  large  swamps  were  formed.  Vast  layers  of 
this  decayed  material  subsided  gradually  and  were  subjected 
to  the  high  temperature  of  the  interior  of  the  earth  and  the 
tremendous  pressure,  also,  of  the  material  on  top  of  them. 
Under  these  circumstances,  the  mass  lost  its  water  and  gases, 
and  changed  to  coal.  Where  the  process  took  place  for  a 


COAL,  SOFT  AND  HARD  193 

short  time,  lignite  was  formed.  After  a  longer  time  bitu- 
minous coal  resulted,  while  anthracite  coal  is  the  result  of 
complete  change. 

In  peat  bogs  we  have  a  form  of  very  impure  carbon,  yet 
peat  may  be  dried  and  burned.  There  are  factories,  also, 
where  peat  is  ground  up,  mixed  with  petroleum,  and  then 
compressed  into  blocks.  This  produces  an  economical  fuel. 

Anthracite  coal  is  almost  pure  carbon,  and,  if  heated,  gives 
off  but  very  little  gas.  Therefore  this  coal  burns  almost 
without  flame.  See  Section  10,  Flames.  Since  the  process 
of  natural  destructive  distillation  has  not  gone  as  far  in 
the  case  of  bituminous  as  of  anthracite  coal,  the  former  sets 
free  a  large  amount  of  gas  when  heated,  and  burns  with  a 
smoky  flame.  Bituminous  coal  is  used  to  manufacture  coal 
gas.  See  Section  28,  Destructive  Distillation. 

Coal  is  not  affected  by  acids,  but  is  attacked  quite  vigor- 
ously by  the  oxygen  of  the  air.  This  is  especially  true  of 
bituminous  coal,  and  spontaneous  combustion  often  takes 
place  in  piles  of  coal  where  the  ventilation  is  poor. 

References :  — 

1.  1205:352-354.  How  Coal  was  Made. 

2.  1407:341-342.  Coal. 

3.  1702:48.  Coal. 

4.  1710:28-29.  Coal, 
a.    1203:226-230.  Coal. 

6.  1204 :  38-45.  The  Coal-making  Time  in  North  America, 

c.  1206  :  460-463.  How  Coal  was  Made. 

d.  1210 :  301-311.  Origin  of  Coal  and  its  Varieties. 

e.  1701:199.  Coal. 
/.  1704:168-169.  Coal, 
flf.  1705:186-187.  Coal. 
h.  1706:184-187.  Coal. 
i.  1707:183-184.  Coal. 

o 


194          INTRODUCTION  TO  GENERAL  SCIENCE 

j.    1708:90-92.  Coal. 

k.    1709:228-230.  Coal. 

I.    1711:272-273.  Coal. 

m.  1712  :  256-259.  Coal. 

138.    PETROLEUM  AND  NATURAL  GAS 

,  The  source  of  petroleum  and  natural  gas  is  organic  matter, 
both  animal  and  vegetable,  which  has  accumulated  in  vast 
masses.  This  material  subsided  like  the  coal-producing 
material,  and  was  subjected  to  tremendous  pressure,  together 
with  very  high  temperature.  By  chemical  change,  and  a 
process  of  natural  distillation,  this  matter  was  changed  to  oil 
and  gas,  both  of  which  have  collected  in  large  pockets.  On 
account  of  the  stratification  of  the  rocks,  an  oil  well  must  be 
drilled  through  certain  layers  until  a  pocket  is  reached. 
Then,  if  there  is  pressure  upon  the  oil,  due  to  its  own  weight 
or  to  gaseous  pressure,  the  oil  will  gush  or  flow  out ;  other- 
wise, pumps  must  be  used  to  obtain  it. 

References :  — 

1.  1205:330-331.  Petroleum  and  Natural  Gas. 

2.  1601 : 20.  Origin  of  Mineral  Oil  and  Natural  Gas. 

3.  1702:  109-113.  Petroleum  and  Mineral  Oils. 

4.  1703:411-412.  Petroleum  and  Refining. 

5.  1710  :  51-53.  Distillates  from  Petroleum. 

a.  1201 :  97-102.  The  Story  of  Petroleum. 

b.  1203  :  230-231.  Petroleum  and  Natural  Gas. 

c.  1204  :  219-222.  Petroleum  and  its  Products. 

d.  1206:166-183.  Liquid  and  Gaseous  Sunlight. 

e.  1208:82-84.  The   Relation  between  Coals   and  Bitu- 

mens. 

/.    1210 :  313-315.     Petroleum  and  its  Origin. 
g.    1306  :  425-426.     Natural  Gas  and  Petroleum. 
h.    1308 :  307-309.     Petroleum  and  Natural  Gas. 
i.    1706 : 207-209.     Petroleum. 


HOW  MOUNTAINS  ARE  MADE  195 

Experiment  71.  —  Distillation  of  Petroleum. 

Apparatus :  Hard  glass  test  tube  8"  X  I",  cork  stopper, 
with  one  hole,  to  fit,  glass  tube  \"  bent  at  right  angles,  four 
U -tubes  having  side  tubes,  cork  stoppers  to  fit,  rubber  tubing 
to  connect  glass  tubing  and  U -tubes,  ring  stand,  burner,  bat- 
tery jar,  6"X8". 

Materials:    Crude  petroleum. 

a.  Fill  hard  glass  tube  one  fourth  full  of  crude  petroleum, 
and  connect  it  to  the  U -tubes  with  pieces  of  rubber  so  that  the 
distillates  will  have  to  pass  through  one  after  the  other.     Put 
the  U-tube  which  is  farthest  from  the  heat  in  a  battery  jar 
filled  with  water  about  20°  C.     Leave  the  free  side  tube  of 
this  last  U-tube  open  to  the  air. 

b.  Heat  the  petroleum  very  gently  at  first,  and  then  more 
strongly.     The  material  which  has  the  lowest  boiling  point 
will  go  the  farthest  before  it  condenses.     Continue  to  heat 
until  the  petroleum  solidifies,  and  then  disconnect  the  hard 
glass  tube  from  the  first  U-tube. 

c.  Break  the  hard  glass  tube,  and  examine  contents.     What 
is  it  ?     Describe  the  various  products  which  you  have  obtained. 
Place  them  in  evaporating  dishes,  or  saucers,  and  try  to  burn 
them.     Compare  them  with  lubricating  oil,  coal  tar,  gasoline, 
and  kerosene. 

139.    How  MOUNTAINS  AKE  MADE 

Mountains  have  been  formed  in  two  general  ways,  folding 
and  faulting.  Both  these  methods,  however,  are  due  to  one 
cause,  the  cooling  of  the  earth.  We  may  consider  the  earth, 
like  any  other  hot  body,  to  have  cooled  on  the  outside  first. 
The  cooling  of  the  material  inside  continued,  and  at  the  same 
time  the  contraction  which  accompanies  cooling  took  place. 
Thus  the  outside  crust  became  loose  and  was  not  in  close 


196          INTRODUCTION  TO  GENERAL  SCIENCE 

contact  with  the  inside  sphere.  Under  these  conditions, 
waves  and  billows  in  the  surface  of  the  crust  would  be  formed, 
producing  vast  folds.  These  folds  formed  mountains,  which 
have  been  worn  by  erosion  until  we  can  see  many  of  the  layers 
bent  and  twisted.  If,  however,  there  were  weak  spots  in  the 
surface  of  the  earth's  crust,  one  part  would  slip,  leaving  the 
rest  elevated.  The  part  remaining  in  its  original  position 
would  form  a  mountain.  We  called  this  process  faulting. 

References :  — 

1.  1205:210-211.  Folded  Mountains. 

2.  1304 : 99-101.  Cause  and  Types  of  Mountains, 
a.    1203  :  45-49.  How  Mountains  May  Be  Formed. 
6.    1206  :  322-328.  Cause  of  Mountain  Growth. 

c.  1209 :  256-257.  Origin  of  Mountain  Ranges. 

d.  1210 :  238-246.  Mountains  —  their  Origin  and  Structure. 

e.  1301 :  337-343.  Development  and  Cause  of  Mountains. 
/.  1302  : 191-193.  Formation  of  Mountains. 

g.  1303  :  178-180.  Formation  of  Block  Mountains. 

h.  1305  :  248-253.  Formation  and  Erosion  of  Mountains. 

i.  1306  : 362-364.  The  Origin  of  Mountains. 

j.  1307  :  71-75.  Folded  and  Block  Mountains. 

k.  1308 :  50-51.  Origin  and  Erosion  of  Mountains. 

I.  1309  :  86-89.  Formation  of  Mountains. 

ra.  1310 :  284-286.  Types  of  Crystal  Deformation. 

140.    THE  SOURCE  OF  FOOD  —  THE  SOIL 

Vegetable  food  must  always  be  the  real  source  of  our  energy 
and  sustenance.  While  meat  forms  part  of  our  diet,  as  well 
as  vegetables  and  fruits,  yet  we  must  realize  that  our  meat- 
producing  stock  lives  upon  grains  and  other  plant  growths. 

Thus  we  must  in  the  end  depend  upon  those  who  will  till 
the  soil.  Moreover,  if  these  agriculturists  would  only  realize 
the  nobility  of  their  profession,  would  study  and  put  into 


THE  FARM  A    WORKSHOP  197 

practice  what  they  learned,  they  would  be  carrying  out  a 
system  of  work  which  is  unequaled  in -its  opportunities  for 
original  research,  and  in  which  experiments  show  results  very 
quickly  in  every  line  of  action.  All  growth  is  dependent 
upon  the  soil;  therefore  we  shall  begin  with  this  part  and 
carry  the  study  through  a  consideration  of  plants  to  animal  life. 
Soil  is  made  by  two  general  agents:  those  which  have  no 
life,  which  we  call  the  inorganic,  under  which  come  water, 
air,  and  winds;  the  others  organic,  including  microorganisms, 
and  larger  plants  and  animals.  We  are  not  likely  to  appre- 
ciate fully  the  amount  of  work  that  is  being  done  to  improve 
our  soil,  but  rather  to  think  only  of  the  damage  done  to  a  few 
of  our  plants  by  the  same  agents.  See  Section  131,  Disin- 
tegration due  to  Plant  and  Animal  Life. 

References :  — 

1.  1205 : 19-22.  The  Soil  and  its  Production. 

2.  1304 :  338.  Importance  of  Soil. 

3.  1503  :  91.  Composition  of  Soil. 

4.  1601 :  31-36.  Relation  of  the  Soil  to  Organic  Evolution. 

5.  1605  :  75-78.  What  Soil  Is. 

a.  1202  :  345-349.  The  Chemical  Nature  of  Soil. 

6.  1603  : 1-6.  The  Origin  of  the  Soil. 

c.  1604 :  29-40.  Soil  Makers. 

d.  1606  :  17-22.  How  Soils  are  Made. 

e.  1607  :  49-52.  Nature  and  Origin  *of  Soil. 
/.  1608 :  16-18.  The  Sunlight. 

g.    1611 :  18-33.         The  Soil:    How  Made  and  from  What. 
h.   1612  :  23-32.         What  we  Find  in  Soils. 

141.    THE  FARM  A  WORKSHOP 

The  farm  should  be  considered  as  a  factory  in  which  the 
farm  products  are  manufactured.  It  is  just  as  impossible 
in  farming  to  get  something  for  nothing  as  it  is  in  any  other 


198          INTRODUCTION  TO  GENERAL  SCIENCE 

business.  It  may  be  that  the  land  is  well  stocked  with  all 
the  material  necessary  to  produce  a  healthy  growth  of  all 
kinds  of  crops,  and  so  the  farmer  may  go  on,  year  after  year, 
without  taking  any  care  of  his  land.  Sooner  or  later,  however, 
the  time  will  come  when  all  the  valuable  plant  food  has  been 
removed  from  the  land,  and  it  becomes  worthless.  This  is 
the  cause  of  many  an  abandoned  farm.  If,  however,  the 
farmer  returns  to  the  soil  those  elements  and  combinations 
of  elements  which  have  been  removed  by  the  particular 
crop  which  he  has  just  harvested,  the  land  will  remain  in  a 
proper  condition.  Nowadays  the  farmer  can  have  access  to 
books  in  which  are  given  tables  that  show  just  what  kind 
of  plant  food  is  necessary  for  each  kind  of  crop,  and  just  how 
much  of  each  material  is  taken  away  for  every  ton  of  harvested 
crop.  He  may  then  know  just  how  much  material  he  must 
return  to  the  soil.  Thus  some  crops,  e.g.  wheat,  require  a 
large  amount  of  phosphorus,  and  that  plant  food  must  be 
returned  to  the  soil,  or  it  will  be  impossible  to  raise  another 
crop  of  wheat,  unless,  as  has  been  mentioned,  there  is  a  large 
store  of  phosphorus  in  the  land.  It  must  be  remembered, 
however,  that  it  is  poor  economy  to  exhaust  the  natural 
fertilizer  of  the  soil,  for  the  commercial  fertilizer;  that  is, 
any  fertilizer  made  by  man  is  not  as  readily  assimilated  by 
the  plants  as  the  natural  plant  food*  There  are  three  gen- 
eral kinds  of  plant  food:  nitrogen,  phosphoric  acid,  and 
potash. 

References :  — 

1.  1601 :  3.  The  Business  of  Farming. 

2.  1605  :  380-383.     Farm  Records  and  Accounts. 

a.  1604  :  4.  The  Meaning  of  the  Word  Farm. 

b.  1606:11.         Agriculture  and  Business. 

c.  1713:150.       Field  Trials. 


RESOURCES  OF  THE  SOIL  199 

142.    RESOURCES  OF  THE  SOIL 

By  resources  is  meant  not  only  the  plant  food  as  such,  but 
the  total  amount  of  surface  material  which  can  be  changed 
into  plant  food  by  nature,  or  by  man.  It  is  a  great  advantage 
that  most  of  the  plant  food  is  still  locked  up  by  nature, 
otherwise  man,  in  his  rapacity,  would  have  deprived  the  soil 
of  its  usefulness  hundreds  of  years  ago. 

Nature  maintains  the  fertility  of  the  soil  by  returning  to 
the  ground  the  decayed  plant  material.  Man  has  done  what 
he  can  to  deplete  the  resources  of  the  soil  by  removing  from  it 
all  the  plant  growth.  Yet,  as  the  farmer  becomes  more 
educated  in  his  own  work,  he  is  gradually  copying  nature 
and  considers  the  land  as  a  factory,  rather  than  as  a  place 
from  which  he  can  get  something  for  nothing. 

The  useful  constituents  of  the  soil  are  carbon,  sulphur, 
oxygen,  phosphorus,  calcium,  soluble  silicates,  and  a  few  other 
chemicals,  which  do  not  enter  into  the  plant  growth  to  any 
great  extent.  We  are  often  misled  by  a  chemical  analysis 
of  the  soil,  for  it  shows  the  total  amount  of  material  present 
in  the  soil,  without  stating  whether  that  material  is  available 
for  plant  food.  Thus,  chemical  analyses  may  show  a  soil 
to  be  rich  in  everything  that  goes  to  produce  plants,  and  yet 
it  may  be  incapable  of  sustaining  plant  life.  What  we  are 
interested  in  chiefly  is  the  amount  of  available  plant  food  — 
that  is,  the  food  which  the  plants  can  obtain  readily  from  the 
ground.  Fertilization  of  the  land  is  the  addition  of  the  miss- 
ing constituents  of  plant  food.  Besides  supplying  definite 
wants,  foreign  fertilizing  material  has  the  further  effect  of 
in  some  way  stimulating  the  plants. 

There  is  another  resource  of  the  soil  which  is  coming  more 
and  more  to  be  reckoned  as  the  chief  cause  of  plant  growth. 


200          INTRODUCTION  TO  GENERAL  SCIENCE 

This  is  the  incalculable  amount  of  bacteria  present.  These 
bacteria  serve  many  purposes  of  disintegration  and  decay, 
and  are  also  able  to  abstract  the  nitrogen  of  the  air,  and 
change  it  into  nitrates,  which  are  then  readily  absorbed  by  the 
plants.  A  little  later  we  will  take  up  a  more  complete  study 
of  bacteria  in  relation  to  plant  growth. 

References :  — 

1.  1601 :  36-37.  The  Soil  a  Laboratory. 

2.  1601 :  76-88.  Chemical  Constituents  of  the  Soil. 

3.  1601 : 101-106.          Store  of  Plant  Food. 

4.  1605  : 109-113.  Plant  Food  in  Soils. 

5.  Farmers'    Bulletin,    No.    342 : 5-10.     Conservation    of    Soil 

Resources. 

a.   1602 :  39.  Make-up  of  Rich  Soil. 

6.    1606 : 18-22.  The  Organic  Elements  and  Agents. 

c.  1606  :  25-28.  Resources  of  the  Soil. 

d.  1610 :  35-36.  Natural  Strength  of  Soils. 

e.  1611 : 141-142.  Soil  Bacteria. 

/.    1612 :  62-70.         How  Plant  Food  is  Preserved. 

g.   1612:71-78.         Getting    Acquainted    with    Plant    Food, 

Chemical  Analysis. 
h.   1713 : 149-150.     The  New  Theory  of  Liebig. 

143.    KINDS  OF  SOILS 

Soils  are  classified  according  to  the  labor  which  is  required 
to  work  them  properly  and  in  respect  to  their  water-holding 
capacity.  Thus  graded,  soils  are  called  heavy,  compact, 
sandy,  light,  porous,  cold,  and  warm.  There  is  another 
classification  which  is  due  to  the  composition  of  the  soils; 
namely,  gravelly,  loamy,  swamp,  peat,  or  humus  soils. 

References :  — 

1.  1205:19-22.  The  Soil. 

2.  1503:91-92.  Kind  of  Soil  Favorable  to  Evaporation. 


TRANSPORTATION  OF  SOILS  201 

3.  1601 :  64-68.  Humus  Soils. 

4.  1601 :  99-101.  Kinds  of  Soils. 

5.  1605  :  78-79.  How  Soils  are  Named. 

6.  Farmers'  Bulletin  No.  408 :  38-40.     Classification  of  Soils, 
a.    1202  :  345-359.     Chemical  Nature  of  Soils. 

6.  1202  :  371-372.  Kinds  and  Classification  of  Soils. 

c.  1203:238-240.  Varying  Characteristics  of  Soils. 

d.  1206:120-121.  The  Soils. 

e.  1312 :  402-403.  Soil  and  its  Varieties. 
/.  1608:25-28.  Other  Classes  of  Soils. 
g.  1608 :  33-37.  Types  of  Soils. 

h.   1610 :  23-28.         Classification  of  Soils. 

144.    TRANSPORTATION  OF  SOILS 

If  we  examine  the  surface  soil  and  the  lower  layers  of  soil, 
we  are  liable  to  find  that  they  are  entirely  different.  This 
indicates  that  the  soils  have  been  brought  from  some  other 
place  and  deposited.  Soils  do  not  always  stay  where  they  are 
formed. 

The  factors  which  enter  into  transportation  of  soils  are 
wind,  water,  and  earthworms,  together  with  other  lower 
organisms.  Rivers  carry  an  immense  amount  of  soil-making 
material,  and  often  deposit  it,  thus  changing  the  river's 
course.  This  alluvial  soil  is  one  of  the  richest  which  we  have. 
Rain  wears  away  hills  and  mountains  and  supplies  the  rivers 
with  their  burden  of  soil.  In  colder  climates,  as  we  have 
learned,  the  frosts  break  up  the  soil  and  loosen  it,  preparing 
it  to  be  washed  away  by  the  rain.  In  larger  masses  of  ice, 
namely,  glaciers,  enormous  transportation  of  rock  and  soil 
takes  place.  We  can  see  this  where  there  have  been  glaciers 
in  prehistoric  times,  and  can  realize,  on  account  of  the  actual 
mountains  of  material  which  they  have  left,  that  their  load 
must  have  been  tremendous.  Winds  also  move  the  soil  of 


202 


INTRODUCTION   TO  GENERAL  SCIENCE 


the  lighter  varieties,  forming  sand  dunes  which  often  over- 
whelm the  fertile  soils  underneath,  although,  in  time  the 
sand  itself  will  make  good  soil. 

The  transportation  of  soil  by  organisms  has  not,  until 
lately,  been  fully  appreciated.  The  amount  of  earth  which 
is  brought  up  by  the  earthworms  is  almost  incredible,  but 
most  of  us  are  familiar  with  the  disturbance  of  the  ground  by 
moles  and  gophers.  There  are  still  smaller  organisms,  which 
are  invisible,  that  cause  the  material  of  which  the  soil  is 
composed  to  be  more  readily  disintegrated,  and  carried  away 
by  the  other  forces.  Plants  also  move  soils  to  a  certain  extent, 
or  so  loosen  them  that  they  can  be  more  readily  moved  by 
wind  or  water. 


References :  — 

1.  1205:145-147. 

2.  1304:43. 

3.  1601:50-54. 

4.  1601:54-61. 

5.  1601:61-64. 

a.    1302:113-114. 
6.    1303:136-138. 

c.  1305:216-219. 

d.  1309 :  146-150. 

e.  1311:87. 

/.  1604:41-49. 
g.  1604:63-68. 
h.  1606:22-25. 
i.  1612:17-22. 


Transportation  by  the  Wind. 

Residual  and  Transported  Soils. 

The  Work  of  Rain. 

Glacial  Soils. 

Earthworms  as  Soil  Workers. 

Transportation  by  Glaciers. 

The  Wasting  of  the  Lands. 

Transportation  of  Rock  and  Soil. 

Transportation  and  Deposition. 

Transported  Waste. 

Soil  Carriers. 

Field  Laborers. 

Transportation  of  Soils. 

The  Soils  that  Living  Things  have  Made. 


145.    TEXTURE  OF  THE  SOIL 

The  size  of  the  particles  comprising  the  soil  causes  its 
various  textures.  Thus,  if  the  particles  are  large,  the  soil 
is  said  to  be  coarse,  and,  if  they  are  small,  we  call  the  soil  fine. 


TEXTURE  OF   THE  SOIL  203 

We  are  not  so  much  concerned  with  the  size  of  the  particles 
as  we  are  with  the  effects  which  the  various  sizes  produce. 
By  measurement  it  has  been  learned  that  the  smaller  a  particle 
becomes,  the  larger  the  surface  is,  compared  with  its  volume. 
For  that  reason,  a  given  amount  of  soil,  if  fine,  has  a  much 
greater  surface  than  if  it  were  coarse.  Now  water  clings  to 
the  surface,  and  in  a  fine  soil  we  will  find  a  larger  amount  of 
water  than  in  a  coarse  soil.  Yet,  on  the  other  hand,  if  the 
soil  becomes  too  fine,  it  is  liable  to  pack  and  take  on  the  effect 
of  a  rock  rather  than  a  mass  of  soil. 

References :  — 

1.  1205  :  19-20.  The  Soil  Layers. 

2.  1601 :  70-76.  Soil-texture,  and  its  Influence. 

3.  1605  :  76-78.  The  Size  of  Soil  Particles. 

4.  Farmers'   Bulletin  No.    187 : 6-8.     Mechanical   Make-up   of 

Soil. 

5.  Farmers'  Bulletin  No.  266  :  27-28.     Organic  Matter  Affecting 

Texture. 

6.  Farmers'   Bulletin  No.   408  :  39-40.     Porosity  —  the  Water 

Capacity  of  Soils. 

a.   1202  :  367-370.     Physical  Condition  of  the  Soils. 
6.    1404 : 113-116.     Texture  of  the  Soil  and  its  Effects. 

c.  1602:33-35.         The  Ideal  Soil. 

d.  1604  : 125-127.     Texture  of  the  Soil. 

e.  1606:38-41.         What  is  Meant  b£  Texture,  and  its  Im- 

portance. 

/.    1607 :  231-232.     Tillage  to  Modify  Soil  Texture. 
g.    1611 :  62-64.         Soil  Crumbs. 
h.    1612 :  34-43.         Concerning  the  Texture  of  Soil. 

Experiment  72. — Water  Capacity  of  Soils. 

Apparatus :  Five  or  more  argand  lamp  chimneys  in  a  rack 
to  hold  them  vertical  over  the  same  number  of  table  tumblers 
or  beakers,  cheeseoloth  in  squares  3"  X  3",  string. 


204          INTRODUCTION  TO  GENERAL  SCIENCE 

Materials :  Sufficient  sand,  gravel  loam,  peat,  clay,  broken 
stone,  and  samples  of  local  soils,  to  fill  the  chimneys. 

a.  Cover  the  small  end  of  each  chimney  with  cheesecloth, 
and  fill  with  different  materials;  place  tumblers  under  each 
chimney,  and  pour  the  same  amount  of  water  into  each. 
Time  the  flow  of  water  through  each. 

146.    IMPORTANCE  OF  MOISTURE 

'We  are  now  concerned  with  the  importance  of  moisture  to 
the  farmer.  Water,  and  its  uses,  are  treated  under  other 
heads.  Plants  can  only  absorb  their  food  when  it  is  dis- 
solved in  water,  and  the  amount  of  water  is  huge  when  com- 
pared with  the  quantity  of  food  which  is  taken  up  at  the 
same  time.  Then  also,  if  the  soil  is  not  moist,  it  becomes 
hard,  and  the  plants  cannot  force  their  roots  through  it,  in 
order  to  obtain  their  food.  In  addition  to  this,  a  very  large 
percentage  of  all  plants  is  actually  water.  Thus  there  may 
be  very  rich  soils  which  could  support  enormous  growths  of 
vegetation,  if  it  were  not  for  the  fact  that  the  rainfall  is  very 
slight.  Many  of  our  deserts,  where  they  have  been  watered 
artificially,  have  become  the  best  producing  places  on  earth. 

References :  — 

1.  1304 :  337-338.  Importance  of  Moisture. 

2.  1407 :  28.  Absorption  of  Water  by  Roots. 

3.  1503 : 143-146.  Water  Supply  for  Plants. 

4.  1601 : 155-156.  Amount  of  Water  Used  by  Crops. 

5.  1605 :  84-85.  Importance  of  Soil  Water. 

6.  1702 : 155-157.  Water  Content  of  Plants. 
a.   1602 :  21-23.  Plants  and  Water. 

6.    1604 : 124-127.     The  Necessity  for  Moisture. 

c.  1606 :  47-48.         Why  Moisture  is  Important. 

d.  1608 : 43-46.         Kinds  and  Uses  of  Soil  Moisture. 


HOW  WATER  IS  HELD  IN  THE  SOIL  205 

e.    1609  :  38-40.         Importance  of  Moisture. 
/.    1611 :  34-35.         What  Water  Does  in  Soils. 
g.    1611 :  55-59.        Plant  Food  in  Soil  Water. 

147.    How  WATER  is  HELD  IN  THE  SOIL 

In  Section  145,  Texture  of  the  Soil,  we  noted  that  the 
smaller  the  particles  were,  the  more  surface  they  had,  and  the 
larger  amount  of  water  they  could  then  hold.  Water  is  held 
in  the  soil  by  actual  porosity,  just  as  water  is  held  in  a  sponge; 
it  is  also  held  by  capillarity,  in  the  same  way  that  oil  travels 
up  a  lamp- wick.  See  Section  118,  Capillarity.  Finally,  it  is 
held  in  a  chemical  method,  forming  almost  a  compound  with 
the  soil.  This  is  called  hygroscopic  water.  See  Section  122, 
Hygroscopic  Salts.  The  wise  farmer  makes  use  of  these 
characteristics  in  order  that  his  crops  may  receive  sufficient 
water.  This  will  be  considered  under  Tilling  the  Soil,  Sec- 
tions 148-149. 

The  water  which  merely  fills  the  larger  spaces  in  the  soil 
rapidly  passes  away,  soaking  into  the  earth,  and  does  not  enter 
much  into  the  food  supply  of  plants.  The  capillarity  causes 
the  lower  water  to  creep  up  and  keep  the  upper  layers  con- 
stantly moist.  The  hygroscopic  water  is  so  closely  bound  to 
the  soil  that  the  soil  may  feel  perfectly  dry,  although  contain- 
ing considerable  moisture.  Hygroscopic  water,  then,  is  of 
no  value  whatsoever  to  the  farmer. 

References :  — 

1.  1503  :  91-92.  How  Water  is  Held  in  the  Soil. 

2.  1601 :  157-162.  Capacity  of  Soils  to  Hold  Water. 

3.  1605  :  79-81.  Relation  of  Size  of  Particles  to  Water, 
a.    1602  :  17-20.  The  Soil  and  Soil  Water. 

6.    1603  :  10-14.         The  Moisture  of  the  Soil  and  How  it  Moves, 
c.    1604 : 128-129.     The  Movements  of  Water  in  the  Soil. 


206          INTRODUCTION  TO  GENERAL  SCIENCE 

d.  1606 :  48-50.         How  Water  is  Held  in  the  Soil. 

e.  1607 : 129-133.     How  Water  is  Held  in  the  Soil  — Soil  Ca- 

pacity. 

/.    1608 :  43-45.         Kinds  of  Moisture. 
g.    1611:41-45.         How  Water  is  Held  in  the  Soil. 
h.    1612 :  40-43.         Three  Forms  in  which  Water  Exists  in  the 

Soil.     Water-holding  Capacity. 

148.     To   INCREASE  THE    MOISTURE-HOLDING   CAPACITY  — 

TILLING 

The  two  aims  of  the  farmer  are  to  obtain  as  large  an  amount 
of  water  as  possible,  and  to  conserve  this  water.  If  the  soil 
is  left  in  its  natural  condition,  a  large  percentage  of  the  water 
will  run  off,  little  being  absorbed.  To  increase  the  capacity 
of  the  soil  for  holding  moisture,  it  should  be  loosened,  and  left 
rough  to  prevent  this  surface  water  from  running  off,  and  the 
amount  of  humus,  which  will  be  described  later  (Section  153), 
should  be  increased.  The  idea  is  to  render  the  soil  as  porous 
as  possible,  so  that  the  water  may  be  absorbed  rapidly. 
Underdrainage  takes  a  large  amount  of  water  away  from  the 
soil,  yet  it  leaves  the  soil  porous,  thereby  increasing  its 
capillarity,  and  the  water  level,  or,  as  it  is  called,  the  water 
table,  is  maintained  more  nearly  at  the  proper  depth,  than 
without  underdrainage.  Under  these  conditions  the  soil 
causes  the  water  to  rise  from  the  water  table,  and  there  is 
more  water  available  for  the  plants.  Any  tilling,  or  cultivat- 
ing of  the  land,  which  breaks  up  the  soil  into  finer  particles, 
increases  its  moisture-holding  capacity. 

By  tilling  of  the  soil  is  meant  any  artificial  changing  of  the 
surface  of  the  ground,  to  prepare  it  for  planting,  or  to  aid  in 
the  growth  of  the  plants.  The  removal  of  weeds  also  comes 
under  this  heading,  since  they  deprive  the  soil  of  plant  food, 
which  is  thus  lost.  It  is  only  in  modern  times  that  the  ad- 


CONSERVATION  OF   MOISTURE  207 

vantages  accruing  from  the  tilling  of  the  soil  have  been 
fully  appreciated. 

Tillage  may  be  performed  by  the  use  of  a  plow,  cultivator, 
harrow,  spade,  hoe,  rake,  or  any  drag  which  tends  to  break 
up  clods  and  pulverize  the  surface  of  the  soil.  Ordinarily, 
the  terms  tilling  and  cultivating  are  synonymous.  The  wise 
farmer  cultivates  the  soil  after  each  rain,  as  soon  as  the  surface 
dries  sufficiently,  in  order  to  preserve  the  moisture. 

References :  — 

1.  1601 : 157-162.      Capacity  of  Soils  to  Hold  Moisture. 

2.  1601 :  192-194.       Cultivation  and  Harrowing. 

3.  1605  :  87-88.  Dry-land  Farming. 

4.  1605  :  165-166.       Methods  in  Tilling. 

5.  Farmers'  Bulletin  No.  245 :  6-7.     Soil  Moisture  and  Humus. 

6.  Farmers'  Bulletin  No.  266.     Cultivation  to  Retain  Moisture 

in  the  Soil. 

a.    1603  :  6-9.  Tillage  of  the  Soil  —  Origin  of  the  Term. 

6.    1604:60-72.  Field  Laborers. 

c.  1606 :  50-56.  How  the  Moisture-holding  Capacity  may  be 

Increased. 

d.  1606 :  64-72.     Tillage  of  the  Soil. 

e.  1608:56-57.     Benefits,    Advantages,    and     Methods     of 

Tillage. 

/.    1610 :  47-49.     Tillage,  Fall  Plowing,  and  Subsoil  Plowing. 
g.    1611 :  60-69.     Tillage,  and  How  it  is  Performed. 
h.    1612 :  96-98.     The  Increase  of  the  Water-holding  Content. 

149.    CONSERVATION  OF  MOISTURE  —  TILLING 

Water  is  lost  from  the  soil  by  evaporation  from  the  surface 
of  the  ground,  and  from  the  surface  of  plants  growing  in  the 
soil.  While  this  evaporation  from  the  crops  cannot  be  pre- 
vented, and  it  is  not  to  be  desired,  yet  by  the  removal  of  weeds 
we  can  prevent  a  large  unnecessary  evaporation.  As  far  as 


208          INTRODUCTION   TO  GENERAL  SCIENCE 

possible,  all  the  water  of  the  soil  should  be  forced  to  pass  up 
through  the  cultivated  plants,  carrying  with  it  plant  food. 
Any  water  which  passes  out  of  the  soil  through  other  means 
is  a  loss.  The  prevention  of  unnecessary  loss  of  water  is 
called  conservation. 

The  capillarity  of  the  soil  must  be  broken  up,  which  can  be 
accomplished  by  loosening  the  surface,  and  leaving  what  is 
called  a  dry  mulch.  There  are  some  practices  which  seem  to 
produce  the  desired  result,  although  they  cause  loss.  If  the 
land  is  rolled,  it  becomes  wetter,  yet  this  dampness  is  taken 
from  the  lower  soil,  and  when  the  surface  water  has  evapo- 
rated, as  it  will  shortly,  the  land  will  be  much  drier  than  it 
would  have  been  if  left  unrolled.  There  is  considerable  loss 
due  to  the  winds,  as  air  in  motion  is  capable  of  absorbing 
much  more  water  than  still  air.  Therefore  windbreaks, 
which  will  lessen  the  velocity  of  the  wind,  will  tend  to  prevent 
evaporation  from  the  surface  of  the  land. 

The  first  tillage,  in  preparing  the  soil  for  planting,  loosens 
it,  and  exposes  the  under  layers  to  the  action  of  the  air,  and 
also  brings  more  plant  food  to  the  surface.  In  order  that 
plants  may  grow  well,  the  surface  of  the  soil  must  be  rather 
finely  broken  and  loosened,  so  that  the  tender  roots  may 
easily  get  a  start.  After  planting,  the  soil  is  cultivated  chiefly 
to  conserve  the  water,  or  to  cause  the  lower  water  to  rise, 
and  come  within  reach  of  the  plant  roots.  We  learned  that 
moisture  moves  through  soil  by  means  of  capillarity.  Loosen- 
ing the  soil  beneath  the  surface  increases  the  "capillarity,  and 
causes  the  water  to  rise  from  the  lower  levels.  On  the  other 
hand,  tilling  the  surface  of  the  ground  causes  the  pores  to  be 
closed  and  evaporation  is  prevented.  This  surface  layer  of 
finely  pulverized  dry  material  is  called  a  soil  mulch,  and  the 
process  of  its  formation  is  called  mulching.  A  rain  will 


CONSERVATION  OF   MOISTURE  209 

destroy  the  soil  mulch,  leaving  pores  through  which  evapora- 
tion can  take  place  readily.  For  that  reason,  cultivation 
after  a  rain  is  necessary,  if  the  moisture  is  to  be  conserved. 

References :  — 

1.  1601 : 184-202.          The  Conservation  of  Soil  Moisture. 

2.  1605  :  84-85.  Conservation  of  Moisture. 

3.  Farmers'  Bulletin  245 :  8-9.     Effects  of  Tillage. 

4.  Farmers'  Bulletin  266.     Management  of  Soils  to  Conserve 

Moisture. 

5.  Reprint  from  Yearbook  Department  of  Agriculture  for  1908. 

Soil  Mulches  for  Checking  Evaporation, 

a.    1602 :  55-56.  Saving  Soil  Moisture. 

6.    1603 : 10-14.  The  Moisture  of  the  Soil  and  How  it  is 
Retained. 

c.  1606 :  56-57.  Conservation  of  Moisture. 

d.  1610:50-51.  Tillage  Conserves  Moisture. 

e.  161 1 :  46.  How  to  Prevent  Evaporation  by  Mulching. 
/.    1612  :  88-98.  The  R61e  that  Tillage  Plays. 

g.    1612 :  164-175.     Soil  Water :  How  it  is  Lost ;  How  it  may 
be  Held. 

Experiment  73.  —  The  Effect  of  Mulches. 

Apparatus:  Balance,  set  of  weights,  five  glass  chimneys 
which  are  very  large  at  the  bottom,  stoppers  for  the  small 
end  of  the  chimneys. 

Materials:  Loam,  sand,  sawdust,  leaf  mold. 

a.  Stopper  the  small  end  of  the  chimneys,  fill  them  nearly 
full  of  loam,  and  wet  the  loam  with  all  the  water  it  can  hold 
without  water  running  out  of  the  chimneys  when  they  are 
inverted.  Put  a  layer  of  very  dry  loam  half  an  inch  thick  on 
the  top  of  the  wet  loam  in  one  chimney;  a  similar  layer  of 
sand  in  another  chimney;  sawdust  in  the  third  chimney;  leaf 
mold  in  a  fourth.  Put  nothing  on  top  of  the  wet  loam  in 
the  fifth  chimney. 


210          INTRODUCTION  TO  GENERAL  SCIENCE 

Weigh  all  the  chimneys,  with  their  contents,  taking  care  to 
number  them.  Weigh  every  twenty-four  hours,  and  make  a 
table  of  your  results.  State  your  conclusions. 

150.    IRRIGATION  AND  UNDERDRAINAGE 

The  artificial  watering  of  land  is  called  irrigation.  Irri- 
gation is  of  the  utmost  importance,  since  about  two -fifths 
of  the  area  of  the  United  States  is  too  dry  for  farming.  Up 
to  the  present  time,  a  little  over  ten  million  acres  are  irri- 
gated, which  is  a  mere  nothing  compared  with  the  dry  area. 
Proper  irrigation,  that  is,  where  there  are  several  thousands  of 
acres  to  be  irrigated,  must  be  a  national  enterprise,  since  it  is 
impossible  for  communities,  or  even  groups  of  men,  to  com- 
bine in  order  that  they  may  put  into  operation  any  large 
irrigation  system.  Irrigation  should  be  used  where  the  soil 
needs  more  water,  whether  in  a  dry  or  humid  climate.  Al- 
though the  cost  of  irrigation  is  considerable,  yet  the  results 
pay,  for  it  will  give  a  large  pecuniary  gain.  In  this  connec- 
tion it  might  be  well  to  understand  that  the  actual  outlay  of 
money  for  improvements  must  not  be  thought  of  as  expense, 
if  the  returns  justify  the  expenditure.  The  same  is  true  in  the 
fertilization  of  the  soil.  If  the  addition  of  several  hundred 
dollars'  worth  of  fertilizer  produces  enough  extra  crop  to  pay 
for  the  fertilizer  and  give  a  fair  profit,  the  cost  of  the  ferti- 
lizer should  not  be  considered  at  all.  For  the  practical  con- 
sideration of  irrigation  in  field  and  garden,  Farmers'  Bulletin 
No.  138,  written  by  Professor  E.  J.  Wickson,  leaves  little 
unsaid. 

Too  much  water  is  nearly  as  bad  for  plants  as  too  little 
water;  they  will  not  grow  if  the  roots  remain  in  water,  since 
the  necessary  air  is  thereby  excluded  from  them.  Under- 


IRRIGATION  AND    UNDERDRAINAGE  211 

drainage  not  only  improves  land  when  it  is  too  wet,  but  in  the 
dry  time  the  crops  grow  better;  for  they  have  run  their  roots 
down  farther  to  seek  the  dampness,  which  has  been  lowered 
by  the  drainage.  Thus  the  plants  have  more  soil  from  which 
to  draw.  Also,  since  the  land  is  left  porous,  the  water-holding 
capacity  is  increased. 

Drainage  may  take  place  on  the  surface,  as  well  as  from 
underneath.  If  the  land  is  very  cheap,  it  may  not  be  worth 
while  to  go  to  the  expense  of  putting  in  a  system  of  under- 
drainage.  If,  however,  the  land  is  valuable,  underdrainage 
should  by  all  means  be  made  use  of,  not  only  to  save  the 
surface  area,  but  also  to  make  the  tilling  and  planting  more 
convenient. 

References :  — 

1.  1601:253-264.          Farm  Drainage. 

2.  1601 :  269-275.          Irrigation  in  Humid  Climates ;   Cost  and 

Results. 

3.  1605:88-90.  Irrigation. 

4.  1605  :  91-94.  Drainage. 

5.  Farmers'  Bulletin  No.  138.     Irrigation  in  Field  and  Garden. 

6.  Farmers'  Bulletin  No.  158.     How  to  Build  Small  Irrigation 

Ditches. 

7.  Farmers'  Bulletin  No.  187.     Drainage  of  Farm  Lands. 

8.  Farmers'  Bulletin  No.  263.     Practical  Information  for  Begin- 

ners in  Irrigation. 

9.  Farmers'  Bulletin  No.  371.     Drainage  of  Irrigated  Lands. 

a.  1308  :  167-171.  The  Distribution  of  Water. 

b.  1309  :  319-321.  History  of  Irrigation. 

c.  1310  : 134-137.  The  Effects  of  Irrigation. 

d.  1404 : 130-133.  The    Amount    of    Water   for   the    Best 

Effects. 

e.  1602:34-35.        Drainage  Necessary. 
/.    1603  : 15-17.         Draining  the  Soil. 

g.    1606 :  53-54.        Beneficial  Effects  of  Underdrainage. 


212  INTRODUCTION  TO  GENERAL  SCIENCE 

h.  1608 :  50-51.  Drainage  and  Ventilation. 

t.  1610 :  42-43.  Drainage  and  Irrigation. 

;.  1611:49-53.  Irrigation. 

k.  1612 : 152-153.  Draining  the  Land. 

151.   SOIL  Am 

Air  is  necessary  for  plant  growth,  as  well  as  for  animals. 
The  plants  need  it  themselves,  and  the  soil  bacteria  require 
it,  and  must  use  it  in  the  formation  of  the  nitrates.  Then, 
also,  oxygen  is  needed  to  carry  on  some  chemical  changes  of 
decomposition,  as  well  as  to  prevent  the  loss  of  the  nitrate- 
forming  material.  If  the  soil  is  too  wet,  the  air  is  excluded, 
and  for  that  reason,  drainage  is  necessary.  Drainage,  either 
natural  or  artificial,  is  necessary  for  plant  growth. 

The  soil  is  ventilated  by  natural  means,  due  to  the  changes 
of  temperature,  causing  expansion  or  contraction  of  the  air 
in  the  soil;  by  changes  of  barometric  pressure;  and  by  the 
changing  of  the  level  of  the  water  table.  Man  can  accomplish 
much  in  the  direction  of  soil  ventilation  by  underdrainage. 

References :  — 

1.  1601 :  239-244.  Needs  of  Soil  Ventilation. 

2.  1601 :  244-248.          Natural  Process  of  Soil  Ventilation. 

3.  1601 :  248-251.          Ways  of  Influencing  Soil  Ventilation. 

4.  1605  :  94-95.  Importance  of  Soil  Air. 

5.  Farmers'  Bulletin  No.  245 :  7.     Soil  Air. 

6.  Farmers'  Bulletin  No.  408 : 37-38.     Air  Necessary  for  Plant 

Growth. 

7.  Bureau  of  Soils,  Bulletin  No.  73 : 25-30.     Oxidation  in  Soil, 
a.    1207 :  330-331.     The  Atmospheric  Circulation  of  the  Soil. 
6.    1602  :  34.  The  Air  and  Water  in  Soil. 

c.  1607 :  125-127.     Movement  of  Air  Through  Soil. 

d.  1608:52-54.        Soil  Ventilation  and  its  Effects. 

e.  1611:6.  Soil  Air. 

/.    1612 :  36.  Air  Circulation  in  Soils. 


PLANT  FOOD  213 


EXPERIMENT  FOR  THE  TEACHER 

See  Farmers'  Bulletin  No.  408:37.  Air  Necessary  for 
Plants. 

If  the  botanical  side  is  to  be  emphasized  in  the  course,  this 
bulletin  may  be  used  to  great  advantage  as  a  source  of  infor- 
mation concerning  experiments. 

Experiment  74.  —  Air  Necessary  for  Roots.* 

Apparatus :  Two  tumblers,  or  beakers,  125  c.c. 

Materials :    Geranium  cuttings,  sweet  oil. 

a.  Boil  some  water,  to  drive  out  the  air,  cool  it,  and  then  fill 
the  two  glasses  three  fourths  full.  Put  a  cutting  of  geranium 
in  each,  but  cover  the  surface  of  the  water  in  one  glass  with  a 
thin  layer  of  sweet  oil.  Observe  the  growth  of  roots. 

Soil  which  is  too  wet  produces  the  same  result. 

152.    PLANT  FOOD— I 

The  principal  plant  foods  are  nitrogen,  phosphoric  acid, 
potash,  and  substances  called  amendments,  which  tend  to  set 
free  plant  food  already  in  the  soil.  Fertilizers  contain  dif- 
ferent compounds  of  the  above  substances. 

When  we  add  a  fertilizer  to  the  soil,  we  say  that  we  are  im- 
proving the  land.  In  reality,  we  are  not  interested  in  whether 
the  land  is  good  or  bad,  but  we  are  careful  to  see  that  the  com- 
ing plants  will  have  food  enough;  just  as  we  do  not  throw 
food  out  into  the  chicken  yard  to  improve  the  chicken  yard, 
but  to  feed  the  chickens.  There  may  be  a  large  amount  of 
plant  food  already  in  the  ground,  but  unless  it  is  in  a  condi- 
tion in  which  it  can  be  absorbed  by  the  plants,  it  might  as 

*  From  Farmers'  Bulletin  No.  408. 


214          INTRODUCTION  TO  GENERAL  SCIENCE 

well  not  be  there.  The  plowing  of  land  tends  to  bring  up, 
and  expose  to  the  action  of  the  air  lower  layers  of  plant  food, 
and  for  this  reason  it  is  advantageous,  where  the  soil  is  fairly 
thick,  to  plow  quite  deeply. 

Plants  are  unable  to  absorb  the  nitrogen  of  the  air  directly, 
but  must  obtain  it  through  a  solution  of  some  compound, 
which  is  taken  in  through  the  roots.  This  is  true  of  all  plant 
food.  Compare  Leaves,  Section  165.  There  are  certain 
bacteria  that  grow  on  the  roots  of  alfalfa,  beans,  peas,  len- 
tils, cowpeas,  and  other  leguminous  plants,  which  have  the 
power  of  absorbing  the  nitrogen  of  the  air  and  changing  it 
into  some  nitrate,  which  is  then  readily  absorbed  by  the 
plant.  If  these  bacteria  are  not  present,  there  must  be  some 
nitrate  added  to  the  soil,  and  this  is  very  often  sodium 
nitrate.  Barnyard  manure  is  a  rich  source  of  nitrogen. 

Phosphoric  acid  itself  is  not  added  to  the  soil,  but  some 
soluble  phosphate  is  used.  The  plant  takes  what  it  needs. 
The  chief  source  of  phosphoric  acid  is  calcium  phosphate, 
which  has  been  rendered  soluble  by  changing  it  into  a  lower 
phosphate  by  sulphuric  acid,  and  it  is  the  phosphorus  part 
which  is  made  use  of  by  the  plant.  Other  sources  are  barn- 
yard manure,  bone  and  refuse  from  meat-packing  houses. 

Potash  is  necessary  for  the  development  of  plants,  and  plays 
a  large  part  in  the  formation  of  seeds.  The  potassium  does 
not  seem  to  supply  material  for  food  directly,  but  aids  in  the 
changes  and  assimilation  of  the  starches  and  sugars.  Some 
plants  need  much  more  than  others,  but  potash  is  found 
throughout  the  whole  of  every  plant.  Thus  the  ashes  of 
wood  is  a  source  of  potash. 

The  organic  acids  form  salts  with  the  potash  acquired  from 
the  soil,  and  the  amount  formed  shows  the  energy  of  the  plant. 
Since  chlorine  seems  to  be  needed  in  the  changing  of  the  hy- 


HUMUS 


215 


3. 
4. 
.5. 
6, 

7. 

S. 


1601 
1605 
1605 
1605 
1605 


107-134. 

25. 

116-120. 

123-124. 

126. 


drocarbons  into  a  soluble  form,  potassium  chloride  is  best  for 
fertilizing  purposes,  and  this  is  especially  true  during  the 
period  of  fruition. 

References :  — 

1.  1601 :  80-81.  Potassium  in  the  Soil. 

2.  1601 : 101-106.  The  Store  of  Plant  Food. 

Nitrogen  of  the  Soil. 
Potash. 

Nitrogen  and  its  Fixation. 
Phosphorus. 

Lime  as  an  Amendment. 
Farmers'    Bulletin    No.    77 : 7-9.     Chemical    and    Physical 

Effects  of  Lime. 
Sources  of  Plant  Food. 
Root  Tubercles. 
Food  from  the  Soil. 
Enriching  the  Soil. 
Applied  Plant  Food. 
Potassium  in  Plants. 
Sources  of  Plant-food  Elements ;   the  Air 

and  the  Soil. 

Plant  Food  in  Soil  Water. 
The  Elements  that  Plants  Use. 
Available  and  Nonavailable  Plant  Food. 

153.    HUMUS 

Humus  is  composed  of  decayed  vegetable  and  animal  matter 
which,  in  the  natural  humus,  has  accumulated  through  untold 
thousands  of  years.  It  is  what  gives  the  soil  the  dark  color, 
and  is  absolutely  necessary  for  plant  life.  As  has  been  noted, 
it  increases  the  water-holding  capacity,  loosens  heavy  soils, 
and  serves  as  food  for  bacteria,  which  play  such  an  important 
part  in  agriculture. 

Living  upon  the  humus  to  a  great  extent,  the  bacteria  cause 
decay,  and  produce  nitric  acid  from  the  nitrogen  contained  in 


a.  1602: 

53. 

6.  1603: 

33-3  . 

c.  1604: 

139-156. 

d.  1606: 

85-98. 

e.  1608: 

128-135. 

/.  1609: 

211-214. 

g.  1610: 

10-15. 

h.  1611: 

55-59. 

i.  1612: 

52  61. 

j.  1612: 

64-66. 

216          INTRODUCTION  TO  GENERAL  SCIENCE 

the  humus.  This  nitric  acid  acts  upon  some  of  the  insoluble 
compounds  of  the  soil,  changing  them  into  nitrates,  which  are 
readily  absorbed  by  the  plants.  In  the  decaying  humus 
carbon  dioxide  is  liberated,  which  dissolves  more  of  the  min- 
erals, forming  plant  food.  The  humus  also  aids  the  growth 
of  the  nitrogen-fixing  bacteria.  The  study  of  the  bacterio- 
logical influences  upon  agriculture  will  be  considered  under 
Bacteria.  See  Sections  155  and  173. 

A  further  study  of  humus  will  be  taken  up  in  the  considera- 
tion of  green  manures.     See  Section  155. 

References :  — 

1.  1205 :  20-21.  How  Humus  and  Subsoil  are  Mingled. 

2.  1601 :  64-68.  Humus  Soils. 

3.  1601 :  95-96.  Chemical  Constitution  of  Humus. 

4.  1605:95-96  The  Uses  of  Humus. 

5.  Farmers'  Bulletin  No.  78 :  5-7.     Importance  of  Humus. 

6.  Farmers'  Bulletin  No.   192:30.     The  Cumulative  Effect  of 

Barnyard  Manure  in  Producing  Humus. 

7.  Farmers'  Bulletin  No.  245 : 11.     Improving  the  Soil  by  In- 

creasing the  Humus, 

a.  1404 :  107-108.  Humus. 

6.  1602  :  42-43.  Humus  in  the  Soils. 

c.  1603  :  21.  Adding  Humus  to  the  Soil. 

d.  1606:52.  Effects  of  Humus  on  Soil  Water. 

e.  1607:76-77.  Humus. 
/.  1608:31-32.  Humus. 
g.  1610:25.  Humus. 
h.  1611:24-25.  Humus. 

i.    1612 :  286-290.     Getting  Humus  into  the  Soil. 
j.    1713 : 148-149.     The  Humus  Theory. 

154.    ENRICHING  THE  SOIL 

If  the  soil  is  lacking  in  any  of  the  plant  food  which  has  been 
mentioned,  that  material  should  be  added  in  order  to  obtain 


GREEN  MANURES  217 

the  best  results.  The  richness  of  the  soil  may  be  measured  by 
the  amount  of  that  plant  food  which  is  present  in  the  smallest 
degree;  that  is,  the  soil  may  have  plenty  of  potash  and  phos- 
phoric acid,  but  if  it  is  weak  in  nitrogen,  its  value  is  no  greater 
than  is  its  nitrogen  content.  Thus  the  addition  of  nitrogen, 
in  this  particular  case,  would  allow  the  other  plant  food  to 
act  proportionally,  and  the  result  would  be  greater  than  that 
due  to  the  mere  addition  of  the  nitrogen  alone.  Any  addition 
of  plant  food  to  the  soil  is  called  enriching  the  soil. 

The  materials  used  for  enriching  the  soil  are  treated  under 
the  various  paragraphs  concerning  plant  food.  Yet  we  must 
remember  that  humus  is  absolutely  necessary  to  make  plants 
grow  well.  The  best  methods  for  increasing  the  humus  con- 
tent is  by  the  use  of  green  manures  and  barnyard  manure. 


References:  — 
1.    1601:285-288. 
2.    1605:114-128. 
3.    1901  :  117-118. 
4.   Bureau    of    Soils, 
Modern  Idea  of 
a.    1603:18-21. 
6.    1606:77. 
c.    1606:83-84. 
d.    1610:41-44. 
e.    1611:147-148. 
/.    1902:57-65. 
g.    1902:111-117. 

Texture  of  Soils  Influenced  by  Fertilizers. 
Materials  Used  as  Fertilizers. 
Bacteria  in  the  Soil. 
Bulletin   No.   73:7-8.       Liebig's  vs.  the 
Fertilization. 
Improving  the  Soil. 
What  Farm  Resources  Are. 
Other  Dressings. 
The  Improvement  of  Soils. 
How  to  Use  Fertilizers. 
Nitrification  and  Bacteria. 
Bacteria  and  Soil  Minerals. 

155.    GREEN  MANURES 

Crops  which  are  grown  for  the  purpose  of  being  plowed 
under,  are  called  green  manures.  Cowpeas,  crimson  clover, 
and  various  legumes  are  used  for  this  purpose,  and  the  result 
is  twofold :  the  supply  of  humus  is  increased,  and  the  nitro- 


218          INTRODUCTION  TO  GENERAL  SCIENCE 

gen  is  obtained,  both  from  the  bacteria  of  decay  acting  on 
the  green  manures,  and  from  the  nitrogen-fixing  bacteria  which 
have  grown  on  the  roots  of  these  plants.  Green  manures  are 
the  only  salvation  for  the  land  when  it  has  run  out  completely. 
Green  manures  need  not  interfere  with  the  regular  crops, 
unless  the  land  is  very  poor,  for  they  may  be  planted  in  the 
fall  or  early  spring,  as  catch  crops,  being  plowed  under  before 
planting  the  regular  crop.  It  means  a  little  more  labor  to  the 
farmer,  but  in  no  other  way  could  he  get  so  much  return  for 
the  time  he  spends  in  thus  increasing  the  available  plant  food. 

References :  — 

1.  1601 :  190-192.          Early  Seeding  and  Catch  Crops. 

2.  1605 :  147.  Green  Manures. 

3.  Farmers'  Bulletin  No.  245:12-15.     Green  Manures. 

4.  Farmers'   Bulletin  No.   278.     Leguminous    Crops  for  Green 

Manuring. 

5.  Farmers'  Bulletin  No.  374 : 5-7.     Inoculation  and  Lime  for 

Alfalfa. 

6.  Bureau  of  Plant  Industry,  Circular  No.  71.  Legume  Inocula- 

tion and  the  Litmus  Reaction  of  Soils, 
a.    1602  :  45-48.         How  Clover  Helps  the  Farmer. 
6.    1603  :  33-35.         Root  Tubercles. 

c.  1606:78-81.        The   Kinds  and  Management  of    Green 

Manure. 

d.  1607 :  201-202.     Danger  from  Green  Manuring.  • 

e.  1610 :  44-47.         Green  Manuring  and  Suitable  Plants. 
/.    1611 :  141-143.     Green  Manure. 

g.    1612  :  289.  The  Help  from  Green  Manure. 

h.    1902 :  95-110.       Legumes  and  Bacteria. 
i.    1903 :  237-263.     Green  Manures. 

156.    BARNYARD  MANURE 

This  source  of  plant  food  is  by  far  the  most  important  that 
the  farmer  can  apply  to  his  land.     It  has  been  long  known, 


BARNYARD  MANURE  219 

but  its  value  has  not  been  fully  realized.  Even  at  the  present 
time,  many  farmers  do  not  appreciate  the  losses  they  sustain 
when  they  do  not  take  the  proper  care  of  their  barnyard  ma- 
nure. The  value  of  this  dressing  is  sometimes  reckoned  in  the 
amount  of  nitrogen,  potash,  and  phosphoric  acid  it  contains. 
Nevertheless,  this  is  not  the  whole  value,  for  it  can  produce 
large  quantities  of  humus,  which,  decaying,  sets  free  nitrogen, 
and  also  increases  the  necessary  bacterial  life  in  the  soil. 

On  account  of  thoughtlessness  or  ignorance,  fully  one  half 
the  value  of  the  manure  is  lost  by  the  flowing  away  of  the 
liquid  part.  There  is  another  great  loss  by  rain,  or  by  the 
water  flowing  from  the  roof,  where  the  manure  has  been  left 
piled  against  the  building.  The  best  way  to  handle  manure 
is  to  spread  it  as  fast  as  it  is  produced.  If  this  is  impossible  or 
undesirable,  the  manure  should  be  kept  in  a  building  with  a 
cement  floor,  tramped  and  kept  moist  by  some  animals,  and 
then  spread  all  at  once.  The  layer  of  manure  should  be  quite 
thin,  especially  where  it  is  fresh  manure,  as  larger  amounts 
may  destroy  the  plant  life  on  account  of  the  rapid  fermenta- 
tion. In  this  connection  it  is  well  to  note  that  properly  fer- 
mented manure  is  better  for  plants;  the  additional  value  is 
not  great  enough,  however,  to  pay  for  the  very  large  loss 
which  takes  place  during  the  fermentation,  and  it  is  more 
desirable  to  use  smaller  quantities  of  the  fresh  manure. 

References :  — 

1.  1601 :  288-291.          Barnyard  Manure  and  Soil  Moisture. 

2.  1605 :  135-147.          Barnyard  Manure. 

3.  Farmers'  Bulletin  No.  162  :  5-6.     Value  of  Barnyard  Manure. 

4.  Farmers'  Bulletin  No.  192.     Barnyard  Manure, 
a.    1606  :  81-83.         Stable  Manures. 

6.   1608:130-131.     Barnyard  Manure. 
c .    1610 :  54-60.         Barnyard  Manure. 


220          INTRODUCTION  TO  GENERAL  SCIENCE 

d.  1611 :  139-141.     Farmyard  Manure. 

e.  1611 :  216-226.     Handling  Manure  on  the  Farm. 
/.    1612  :  206-215.     Barnyard  Manure. 

g.    1902  :  69-76.         Barnyard  Manure  and  Bacteria. 
h.   1903  :  306-317.     Losses  from  Barnyard  Manure. 

157.    RENOVATION  OF  WORN-OUT  SOILS 

Any  soil  which  has  ever  produced  a  crop  may,  with  care 
and  patience,  be  made  to  produce  again,  just  as  bountifully 
and  perhaps  more  bountifully.  Farmers'  Bulletin  No.  245 
gives  an  excellent  summary  of  the  whole  matter,  as  well  as  a 
general  review  of  many  topics  which  have  been  studied  in  this 
connection. 

References:  — 

1.  Farmers'  Bulletin  No.  245.     Renovation  of  Worn-out  Soils. 

2.  Farmers'  Bulletin  No.  406.     Soil  Conservation. 

3.  Reprint  from   Yearbook  Department  of    Agriculture,    1908. 

Plant  Food  Removed  by  Rain. 

a.   1612 :  282-290.     What  may  be  Done  to   Renovate  Worn- 
out  Soils. 
6.    1606 :  20-22.     Worn-out  Land  Lacks  Humus. 

c.  1902:119-122.     Soil  Inoculation  and  the  Control  of  Soil 

Bacteria. 

d.  1903 : 152-154.     Maintaining  Soil  Fertility. 

158.    THE  LIMING  OF  THE  SOIL 

Lime  corrects  the  acidity  of  the  soil,  and  since  it  liberates 
plant  food,  it  should  be  classified  as  an  amendment  rather 
than  as  a  fertilizer.  See  Section  121,  Acids,  Bases,  and  Salts. 
Soil  may  be  tested  by  blue  litmus  paper.  If  it  turns  red,  lime 
should  be  applied.  It  aids  the  soil  organisms  in  the  fixation 
of  nitrogen,  and  is  necessary  to  obtain  the  best  results  from 
the  use  of  barnyard  manures.  Some  crops  need  more  lime 


THE  LIMING  OF  THE  SOIL  221 

than  others,  and  this  gives  us  a  test  for  the  lack  of  lime.  If 
red  clover  fails  where  it  once  grew,  it  is  a  sure  indication  that 
lime  should  be  applied  to  the  soil. 

The  sources  of  lime  are  limestone  and  gypsum,  but  the 
limestone,  or  calcium  carbonate,  is  more  desirable.  When 
roasted,  this  changes  into  unslaked  lime,  the  material  that  is 
used  on  the  soils.  There  it  unites  with  the  water,  forming 
slaked  lime,  which  is  rather  soluble.  In  this  way  the  lime  can 
be  carried  throughout  the  grains  of  the  soil.  A  small  applica- 
tion of  lime  lasts  for  a  long  time.  On  the  other  hand,  an  ex- 
cess of  lime  does  no  harm. 

In  Section  163,  Plant  Roots,  it  will  be  learned  that  the  roots 
of  growing  plants  give  off  an  acid.  Lime  neutralizes  this 
acid. 

References :  — 

1.  1205:10.  Acids  in  Soil  Water. 

2.  1601 :  30.  Effects  of  Lime  on  Soil. 

3  1605 : 126-128.          Lime,  its  Functions  and  Forms. 

4.  Farmers'  Bulletin  No.  77.     The  Liming  of  Soils. 

5.  Farmers'  Bulletin  No.  259 :  7-9.     Spreading  Lime. 

6.  Farmers'  Bulletin  No.  374 : 5-7.     Inoculation  and  Lime  for 

Alfalfa. 

7.  Bureau  of  Plant  Industry  No.  71.     Legume  Inoculation  and 

the  Litmus  Reaction  of  Soils, 

a.  1603  :  26.  Action  of  Lime  in  ttie  Soil. 

6.  1606  :  97-98.  Lime  as  an  Amendment. 

c.  1607  :  71.  Action  of  Lime. 

d.  1610 :  64-67.  Use  and  Application  of  Lime. 

e.  1611:146-147.  Liming  the  Soil. 
/.  1612 :  99-107.  Liming  the  Land. 

Experiment  75.  —  The  Effect  of  Lime  —  Acid  Soils. 
Apparatus:   Beaker    150    c.c.,   battery  jar  6"X8",   ring 
stand,  burner,  asbestos  mat. 


222          INTRODUCTION  TO  GENERAL  SCIENCE 

Materials :  Calcium  hydrate,  hydrochloric  acid,  5  per  cent, 
blue  and  red  litmus,  samples  of  soil  where  clover  has  been 
growing. 

a.  Take  some  of  the  soil  in  a  battery  jar,  and  add  just  enough 
water  to  cover  it.  Stir  for  a  few  minutes,  and  then  test  the 
water  with  blue  litmus  paper.  If  the  paper  turns  red,  it  in- 
dicates an  acid  soil.  Add  a  little  lime  water,  or  some  slaked 
lime,  to  the  mixture  of  soil  and  water,  stirring  as  before.  Test 
again  with  blue  litmus  paper.  If  the  soil  is  still  acid,  continue 
to  add  lime  until  the  soil  is  neutral. 

6.  If  the  water  in  the  soil  in  (a)  does  not  indicate  an  acid, 
it  may  be  because  the  acid  is  too  dilute.  To  concentrate  the 
suspected  acid,  pour  the  water  from  the  soil  into  beaker,  and 
boil  down  to  one  twentieth  of  its  original  volume.  Then  test 
with  litmus. 

c.  Test  dilute  hydrochloric  acid  with  litmus,  and  then 
neutralize  the  acid  with  lime,  as  in  Experiment  65. 

159.    COMMERCIAL  FERTILIZERS 

The  fertilizers  which  are  on  the  market  are  usually  the 
so-called  complete  fertilizers:  that  is,  they  contain  the  phos- 
phorus, potash,  and  nitrogen  in  the  proportions  which  have 
been  found  best  for  general  crops.  Thus  they  are  not,  per- 
haps, adapted  to  the  particular  crops  which  the  farmer  wishes 
to  raise,  nor  do  they  always  supply  the  plant  food  which  is 
lacking  from  a  particular  field.  It  is  impossible,  then,  for  a 
farmer  to  buy  a  commercial  fertilizer  which  can  be  very  well 
adapted  to  his  special  needs. 

The  losses  which  accrue  from  the  use  of  commercial  fer- 
tilizers are  not  confined  to  this  inadaptability  to  the  farmer's 
needs,  but  also  include  the  transportation  expenses,  and  the 


USE  OF  COMMERCIAL  FERTILIZERS  223 

profits  to  all  those  who  handle  the  fertilizer  before  the  farmer 
receives  it.  Often  a  ton  of  fertilizer  has  no  more  material  in 
it  which  can  be  used  for  the  real  plant  food  than,  perhaps, 
fifteen  hundred  pounds;  the  other  five  hundred  pounds  may 
be  merely  dirt.  This  does  not  cheat  the  farmer,  for  the  fifteen 
hundred  pounds  contain  all  that  he  is  buying,  as  is  shown  by 
the  analysis  of  the  fertilizer.  The  loss  is  due  to  the  fact  that 
the  farmer  must  pay  transportation  expenses  on  five  hundred 
pounds  of  useless  material.  In  addition  to  this,  the  average 
farmer,  instead  of  buying  from  a  wholesaler,  and  saving  un- 
necessary profits,  buys  from  some  small  retailer,  who  not  only 
makes  a  profit,  but  perhaps  does  not  know  much  about  fer- 
tilizers. 

References :  — 

1.  1605:129-131.     Complete  Fertilizers. 

2.  Farmers'  Bulletin  No.  44:8-11.     Need  of  Commercial  Fer- 

tilizers. 

3.  Farmers'  Bulletin  No.  44: 11-22.  Fertilizing  Material. 

4.  Farmers'  Bulletin  No.  79 :  5-7.  Fraud  in  Fertilizers. 

5.  Farmers'  Bulletin  No.  329 : 5-6.  High-grade  vs.  Low-grade 

Fertilizer. 

a.    1602  :  40.  Commercial  Fertilizers. 

6.    1603  :  24-26.  Commercial  Fertilizers. 

c.  1608:128-137.  Fertilizers. 

d.  1610:68-112.  Artificial  and  Concentrated  Manure  and 

Fertilizers. 

e.  1611 :  143-147.     Commercial  and  Mineral  Fertilizers. 
/.    1612  :  227-237.     Buying  Plant  Food  for  the  Soil. 

160.    USE  OF  COMMERCIAL  FERTILIZERS 

Whenever  fertilizers  are  used,  it  must  be  remembered  that 
plants  not  only  require  plant  food,  but  they  require  it  under 
particular  conditions.  Plants  may  die,  even  though  supplied 


224  INTRODUCTION  TO  GENERAL  SCIENCE 

with  plenty  of  available  plant  food,  if  the  conditions  of  the 
soil  are  not  satisfactory.  Ofttimes  the  improvement  of  the 
texture  of  the  soil  would  cause  more  productivity  than  the 
addition  of  any  commercial  fertilizer.  Then,  also,  the  plant 
requires  water,  air,  heat,  and  light;  and  these  conditions  must 
be  supplied  in  sufficient  amount,  if  the  best  results  are  to  be 
obtained. 

When  a  farmer  is  buying  fertilizer,  he  should  realize  that 
the  cost  of  the  labor  of  making  poor  fertilizer  is  just  as  great 
as  in  preparing  good  fertilizer,  and  therefore  the  best  is,  after 
all,  the  cheapest.  There  is  no  kind  of  fertilizer  which  improves 
the  soil  as  well  as  barnyard  manure.  Fertilizers  as  a  rule  do 
not  increase  the  organic  matter  in  the  soil.  The  manure 
increases  the  amount  of  humus,  supplies  food  for  bacteria, 
actually  places  bacteria  in  the  soil,  and  contains  the  necessary 
plant  food. 

References :  — 

1.  1605:129-131.     Complete  Fertilizers. 

2.  Farmers'  Bulletin  No.  44  : 28-33.     Principles  Governing  Use 

of  Fertilizers. 

3.  Farmers'   Bulletin  No.  259 : 5-6.     Use  of  Commercial  Fer- 

tilizers. 
a.   1606 :  98-100.     Commercial  Fertilizers. 

161.    HOME-MIXED  FERTILIZERS 

The  great  advantage  of  mixing  fertilizers  at  home  is  that 
the  farmer  knows  what  is  in  the  fertilizer,  and  avoids  all 
danger  of  fraud.  There  is  another  advantage  which  comes 
through  cooperation,  for,  if  he  combines  with  his  neighbors, 
he  may  procure  the  material  in  very  large  quantities,  obtain 
carload  freight  rates,  and  produce  a  fertilizer  with  home  labor 
very  much  more  cheaply  than  the  cheapest  and  poorest 


FERTILIZERS  FOR  GARDEN  CROPS  225 

fertilizer  can  be  obtained  in  the  market.  Not  only  that,  but 
he  can  adapt  the  fertilizer  to  his  particular  needs,  and  to  the 
varying  needs  of  the  different  parts  of  his  farm.  He  will 
learn  to  experiment,  and  not  to  be  satisfied  with  some  partic- 
ular kind  of  fertilizer  just  because  others  have  said  it  is  good. 
He  buys  no  waste  material,  and  so  reduces  the  cost  of  trans- 
portation. The  farmer  becomes  a  scientific  farmer,  and  puts 
more  thought  toward  the  production  of  better  results. 

References :  — 

1.  1605:131-132.     Home-mixing  of  Fertilizers. 

2.  Farmers'  Bulletin  No.  44 :  22-27.   Agricultural  vs.  Commercial 

Value  of  Fertilizers. 

3.  Farmers'  Bulletin  No.  44 :  27-28.  Home-mixed    Fertilizers. 

4.  Farmers'  Bulletin  No.  222  :  5-9.     Home-mixing  of  Fertilizers. 

5.  Farmers'  Bulletin  No  320 :  5-9.     Fish  Fertilizer. 

162.    FERTILIZERS  FOR  GARDEN  CROPS 

The  different  garden  crops  respond  differently  to  the  same 
fertilizer,  or,  to  put  it  another  way,  different  crops  require 
different  fertilizers.  So  many  special  examples  are  given  in 
the  Farmers'  Bulletins  that  there  will  be  no  mention  here, 
and,  moreover,  the  question  is  not  a  general  one.  Plants 
seem  to  react  to  fertilizers  as  persons  do  to  medicines.  Both 
fertilizers  and  medicines  do  not  observe  scientific  laws,  in  the 
exactness  of  their  action,  but  may  require  experimentation. 
There  is  this  difference,  however:  all  plants  of  the  same 
species  react  alike  to  a  given  fertilizer;  with  persons,  each 
individual  is  a  special  case  in  his  reaction  to  medicines. 
References :  — 

1.  Farmers'   Bulletin   No.   105:12-13.    Fertilizers  for   Garden 

Crops. 

2.  Farmers'  Bulletin  No.  162 :  6-9.     Nitrate  of  Sodium  for  Gar- 

den Crops. 


226          INTRODUCTION  TO  GENERAL  SCIENCE 

3.  Farmers'  Bulletin  No.  222 :  7-9.       Formulas  for  Fertilizers. 

4.  Farmers'  Bulletin  No.  255 :  11-12.     Fertilizers  for  the  Garden. 

5.  Farmers'    Bulletin,   No.    278 : 14.     Crops    to   Follow   Green 

Manure. 

163.    PLANT  ROOTS 

The  use  of  roots  is  to  hold  the  plant  erect  and  to  supply  it 
with  plant  food,  which  is  dissolved  in  soil  water.  The  process 
by  which  plant  food  is  absorbed,  is  called  osmosis,  and  the 
pressure,  which  is  produced  in  the  plant,  is  called  osmotic 
pressure.  See  Section  119,  Osmosis.  Roots  grow  down- 
ward on  account  of  gravity,  but  later  they  also  grow  in  the 
direction  of  moisture.  The  length  of  the  root  system  of  a 
single  plant  may  run  into  miles,  but  the  fine  root-hairs  die, 
only  to  be  replaced,  in  a  few  days,  by  thousands  of  new  ones. 

Roots  excrete  a  material  which  is  capable  of  dissolving  some 
of  the  insoluble  plant  food  in  the  soil.  The  excretion  may 
become  harmful  to  the  plant,  however,  and  this  is  one  of  the 
arguments  in  favor  of  rotation  of  crops,  since  each  plant  pro- 
duces a  different  excretion,  which  does  not  seem  to  harm 
other  plants.  The  effect  of  this  excretion  may  be  neutralized 
by  the  addition  of  lime.  See  Section  121,  Acids,  Bases,  and 
Salts. 

References :  — 

1.  1304 :  40-41.  The  Work  of  Roots. 

2.  1407  :  19-33.  Roots. 

3.  1503  :  82-97.  Roots  and  their  Work. 

4.  1605  :  64-65.  How  the  Plant  Gets  its  Food. 

5.  1702 :  242.  Osmosis  in  Roots. 

6.  1702  :  312-313.  Roots  and  Tubers  as  Food. 

7.  Bureau    of    Soils,    Bulletin   No.    73 : 17-25.     Oxidation   and 

Reduction  by  Roots, 
a.    1401:36-61.     Roots. 


PLANT  STEMS  227 

6.  1402 :  64-73.  How  the  Plant  Takes  in  the  Soil  Water. 

c.  1404 :  87-162.  The  Work  of  Roots. 

d.  1405:31-44.  Roots. 

e.  1406 :  120-125.  Function  and  Structure  of  Roots. 
/.  1603 :  27-40.  The  Soil  and  the  Water. 

g.    1604:124-138.     Roots. 

h.    1902:98-101.       Root-tubercle  Bacteria. 

Experiment  76.  —  Effect  of  Plant  Roots  on  Soil. 

Apparatus:    Saucer,  cloth. 

Materials:  Radish  seeds,  litmus  paper  (blue),  blotting 
paper,  distilled  water. 

a.  Place  a  piece  of  blue  litmus  paper  upon  the  saucer,  and 
on  it  place  several  radish  seeds.  Cover  the  seeds  with  an- 
other piece  of  blue  litmus  paper,  and  place  over  the  latter  a 
piece  of  blotting  paper.  Moisten  all  of  the  paper  with  dis- 
tilled water,  and  cover  with  a  dry  cloth.  Moisten  each  day, 
if  necessary,  and  note  any  change  in  the  litmus  paper.  What 
are  your  conclusions  ? 

164.    PLANT  STEMS 

The  purpose  of  the  stem  is  to  hold  up  the  leaves  and  flowers 
to  the  light,  and  to  supply  them  with  the  materials  for  plant 
food.  Some  stems  also  store  food,  after  it  has  been  made 
by  the  leaves,  while  the  stems  of  a  few  plants  aid  in  the  mak- 
ing of  the  food.  The  propagation  of  some  plants  is  produced 
by  their  stems.  The  main  stems,  since  strength  is  required, 
tend  to  become  woody,  and  in  trees  serve  as  a  source  of  wood. 

Stems  are  composed  of  bundles  of  very  fine  tubes  through 
which  the  sap  rises,  partly  on  account  of  capillarity  (see 
Section  118),  and  partly  due  to  the  osmotic  pressure  of  the 
roots.  See  Section  119,  Osmosis.  The  complete  explana- 
tion of  the  movement  of  sap  is  not  known. 


228          INTRODUCTION  TO  GENERAL  SCIENCE 

References :  — 

1.  1407:40-69.  Stems. 

2.  1407:71-79.  Work  of  the  Stem. 

3.  1503 :  98-121.          Buds  and  Stems. 

4.  Farmers'  Bulletin  No.  173 :  8, 11-14.     Wood  and  its  Structure. 

5.  Farmers'  Bulletin  No.  181.     Pruning. 

a.  1401 :  83-103.  Structure  of  the  Stem, 

fc.  1402:14-18.  Stem. 

c.  1404 :  224-285.  The  Work  of  the  Steins. 

d.  1405:49-63.  Stems. 

e.  1406 :  142-148.  Stem  Forms  and  Uses. 
/.  1505:49-72.  The  Stem. 

g.    1606 : 120-122.    The  Processes  of  Growth. 

h.    1609:282-283.    The  Stem. 

i.    1611 :  86-90.        Stems  and  their  Use. 

Experiment  77.  —  The  Pressure  of  Sap. 

Apparatus:  Tube  \"  diameter,  6'  long,  rubber  tubing 
\"  diameter,  4'  long,  ring  stand  with  clamp. 

Materials:   Growing  plant  in  flower  pot. 

a.  Cut  off  the  plant  a  few  inches  from  the  ground,  and  slip 
the  rubber  tubing  over  the  stump.  Then  insert  the  glass 
tube  in  the  rubber  tubing  and  clamp  to  a  ring  stand.  Fill  the 
tube  with  water  to  the  height  of  three  feet,  and  mark  the  water 
level  with  a  rubber  band.  Does  the  water  rise  in  the  tube  ? 
Where  does  the  extra  water  come  from? 

6.  Nearly  fill  the  tube  with  water.     Does  the  column  still 
rise  ?    What  causes  the  pressure  ? 

165.    LEAVES 

Leaves  manufacture  plant  food  from  the  raw  materials, 
which  have  been  gathered  by  the  roots,  and  transported  by 
the  stems.  Under  the  action  of  the  sun's  energy,  water  from 
the  root,  and  carbon  dioxide  from  the  air,  are  combined  to 


LEAVES  229 

form  starch;  while  oxygen  is  given  back  to  the  air.  The 
starch  is  then  changed  to  grape  sugar  or  glucose  which  com- 
bines with  some  of  the  elements  brought  from  the  ground, 
and  forms  proteids.  Starch  can  only  be  produced  in  sunshine, 
although  the  formation  of  proteids  may  be  performed  in  the 
dark. 

Another  function  of  the  leaf,  which  is  most  important,  is 
the  very  large  evaporation  of  water  from  its  surfaces.  This 
aids  capillarity  and  osmosis,  in  the  rise  of  the  sap,  just  as  the 
burning  of  a  lamp  aids  the  upward  motion  of  the  oil,  by  remov- 
ing the  oil  which  is  at  the  top.  Evaporation  from  a  leaf  is 
called  transpiration. 

References :  — 

1.  1407 :  88-122.  Leaves,  —  Structure  and  Functions. 

2.  1503  :  122-141.  Leaves  and  their  Functions. 
a.    1401:130-149.  Leaves. 

6.  1402  :  90-100.  Leaves  and  Foliage. 

c.  1403  :  24-48.  Leaves. 

d.  1404:163-224.  Work  of  Leaves. 

e.  1405:97-104.  Leaves. 

/.  1406  :  15-33.  The  Leaf  —  its  Uses. 

g.  1505 :  92-105.  Leaves  —  Function  or  Work.] 

h.  1602  :  30-32.  Leaves,  Buds,  Seeds. 

i.  1604 :  157-176.  Leaves  and  their  Work. 

./.  1609:306-314.  Leaves. 

k.  1611 :  72-80.  How  the  Leaf  Gets  Food  from  the  Air. 

Experiment  78.  —  Transpiration. 

Apparatus:  Ring  stand  with  clamp,  beaker  100  c.c.,  glass 
tube  \"  diameter,  8"  long,  beaker  200  c.c.,  tumbler. 

Materials:  Mercury,  wax  (beeswax  90  per  cent,  Venice 
turpentine  10  per  cent),  soil,  olive  oil. 

a.  Cut  a  small  branch  from  a  vigorously  growing  plant  and 
seal  it  in  one  end  of  the  tube  with  wax.  Be  careful  not  to 


230  INTRODUCTION  TO  GENERAL  SCIENCE 

cover  the  cut  part  with  wax,  and  do  not  cut  the  branch  until 
it  is  needed.  Place  the  other  end  of  the  tube,  after  filling  it 
with  cooled  boiled  water,  below  the  surface  of  some  mercury, 
in  the  beaker,  and  clamp  the  tube  on  the  ring  stand.  (After 
Detmer.) 

6.  What  happens  ?  Is  the  mercury  sucked  up  ?  See 
Experiment  44.  Where  does  the  water  go  to  ?  What  pres- 
sure is  produced  ?  See  Experiment  42. 

c.  Place  a  geranium  cutting  in  the  large  beaker,  which  should 
be  three  fourths  full  of  moist  soil.  Cover  the  soil  with  olive 
oil  and  invert  an  ordinary  table  tumbler  over  the  cutting. 
What  do  you  notice  after  an  hour  ?  Does  this  explain  (6)  ? 

166.    BUDS 

Buds  are  of  two  classes,  leaf  and  flower.  Flower  buds  are 
only  produced  where  there  is  a  surplus  of  plant  food  beyond 
that  which  is  necessary  to  supply  the  needs  of  life  and  growth. 
Anything  which  will  check  growth,  without  injuring  the  plant, 
will  cause  flower  buds,  and  therefore  more  fruit.  Advantage 
is  taken  of  this  fact  where  pruning  is  practiced. 

The  bud  contains  the  characteristics  of  the  whole  tree, 
except  that  which  is  below  the  ground ;  and  therefore  we  would 
expect  that,  if  the  bud  could  grow,  it  would  be  similar  to  the 
rest  of  the  tree.  Where  grafting  is  practiced,  this  is  made 
use  of,  since  the  addition  of  buds  to  another  tree  will  produce 
branches  which  are  similar  to  the  bud.  This  is  called  budding. 

References :  — 

1.  1407:80-87.  Buds. 

2.  1503  :  100-102.  Buds. 

3.  1605:227.  Pruning. 

4.  1605:230-233.  Pruning. 


FLOWERS  231 

a.  1401:119-129.  Buds. 

6.  1402:36-41.  Winder  Buds. 

c.  1403  :  19-23.  The  Opening  of  the  Buds. 

d.  1405:85-96.  Buds. 

e.  1406 :  173-186.  Buds  and  Branches. 
/.  1502 :  175-179.  Budding. 

g.  1505  :  111-120.  Winter  and  Dormant  Buds. 

h.  1603  :  54-61.  Plant  Propagation  by  Buds. 

i.  1606 :  163.  Pruning  vs.  Training. 

j.  1609.283-286.  Buds. 

167.    FLOWERS 

The  purpose  of  the  flowers  is  that  of  reproduction.  This 
is  caused  by  the  pollen  of  the  same  flower,  or  of  other  flowers, 
reaching  the  egg  cells,  which  then  grow  into  seeds,  if  plant 
food  is  supplied  them.  This  pollination,  as  it  is  called,  may 
be  accomplished  by  wind,  water,  insects,  gravity,  or  by  a 
bending  in  of  the  part  of  the  flower  which  carries  the  pollen. 
The  latter  is  called  self-pollination.  Cross-pollination,  where 
the  pollen  of  one  flower  comes  in  contact  with  the  egg  cells 
of  another  flower,  is  productive  of  better  results  than  those 
due  to  self-pollination. 

Flowers  are  adapted  to  producing  these  results,  in  as  many 
ways  as  possible,  the  color  and  perfume,  as  well  as  nectar  of  the 
flower,  existing  merely  to  attract  insects.  In  some  cases, 
the  flowers  have  adapted  themselves  to  the  particular  kind  of 
insects  of  that  locality,  and  have  changed  their  shape  so  that 
the  cross-pollination  may  be  accomplished  in  the  best  way. 

References :  — 

1.  1407:123-131.          The  Flower. 

2.  1503:31-49.  Flowers. 

a.  1401 :  197-207.     The  Flower  and  its  Organs. 

b.  1402  : 128-134.     Fertilization  and  Pollination. 


232  INTRODUCTION  TO  GENERAL  SCIENCE 

c.  1403:49-74.  Flowers. 

d.  1403:74-78.  Cross-fertilization. 

e.  1404:286-311.  The  Work  of  Flowers. 

/.  1405 : 159-167.  Flowers  and  Reproduction. 

g.  1406:196-233.  The  Flower. 

h.  1603  :  44-53.  The  Flower. 

t.  1609:315-329.  The  Flower. 

J.  1611 :  91-99.  The  Flower  and  Fruit. 


168.    FRUITS  AND  SEEDS 

After  the  seeds  have  become  formed  and  have  begun  to 
grow,  a  certain  amount  of  protection  is  necessary,  as  well  as 
a  plentiful  supply  of  food.  This  is  accomplished  by  a  nut 
or  fruit,  or  some  other  simple  form  of  covering. 

Since  the  crowding  of  plants  beneath  the  parent  plant  would 
prevent  proper  growth,  a  seed  dispersion  is  necessary.  This 
is  accomplished  by  some  fruits  themselves,  such  as  the  squirt 
cucumber;  or  it  may  be  produced  by  elastic  tissues  of  the 
seed  pods,  or  through  the  agency  of  birds,  animals,  and  water. 
Burrs  and  the  stickers  of  foxtail  are  examples  of  transporta- 
tion through  other  agencies,  and  the  seeds  sometimes  cling 
to  the  feet  of  animals  or  of  birds,  and  are  carried  some  distance 
before  being  dropped.  Wind  transports  fluffy  and  winged 
seeds. 

When  the  seeds  are  in  contact  with  moisture,  osmosis  takes 
place  and  water  passes  into  the  seed.  See  Section  119, 
Osmosis.  After  the  absorption  of  water  the  growth  depends 
upon  warmth  and  plant  food. 

References :  — 

1.  1407:5-11.          The  Seed,  its  Germination  and   Storage  of 

Food. 

2.  1407:146-150.     The  Fruit. 


FRUITS  AND  SEEDS  233 


3.    1503:50-65.              Fruits. 
4.    1605:47-55.               Seeds. 
5,    1702  :  235-240.          Chemistry  of  Plant  Growth,  Seeds. 
6.   Farmers'  Bulletin  No.  157.     The  Propagation  of  Plants. 

7.   Farmers'  Bulletin 

No.  329  :  15-16.     Seed  Selection. 

a. 

1401 

:  5-13. 

The  Seed  and  its  Germination. 

6. 

1401 

:  14-23. 

Storage  of  Food  in  the  Seed. 

c. 

1401 

:  221-227. 

The  Fruit. 

d. 

1402 

:  158-163. 

Dispersal  of  Seed. 

e. 

1403 

:  90-94. 

What  a  Seed  Is. 

/. 

1404 

:  312-325. 

The  Work  of  Fruits. 

9- 

1405 

:  191-199. 

Seed  Dispersion. 

h. 

1406 

:  63-68. 

Fruits. 

i. 

1406 

:  87-107. 

Seeds. 

j. 

1604 

:  190-207. 

Blossom  and  Seed. 

k. 

1604 

:  246-260. 

Seed  Scattering. 

I. 

1604 

:  261-276. 

Seed  Carriers. 

Experiment  79.  —  Seed  Testing  —  Germination. 

Apparatus :  Shallow  box  filled  with  soil,  or  moistened  saw- 
dust,   divided   into   squares   by   strings   crossing  the   box; 
beaker  100  c.c. 

Materials:  Seeds  to  be  tested,  2  sheets  blotting  paper 
6"  X  6". 

a.  Place  some  seeds  in  a  beaker  full  of  water  and  see  what 
happens  to  them  in  a  few  days.  What  do  seeds  need  in 
order  to  sprout? 

6.  Place  some  seeds  in  some  dry  soil.     Do  they  sprout? 

c.  Place  some  seeds  one  fourth  of  an  inch  below  the  sur- 
face of  the  soil  in  the  little  squares,  in  the  box.     Number  the 
squares  and  make  a  note  of  the  seeds  used.     See  how  many 
germinate.     Corn  may  be  tested  in  this  manner  and  the  proper 
kind  of  corn  selected  for  planting. 

d.  Seeds  may  be  sprouted  by  being  kept  between  two  pieces 
of  moistened  blotting  paper.     Try  it. 


234          INTRODUCTION  TO  GENERAL  SCIENCE 

169.    FLAVORING  EXTRACTS  AND  PERFUMES 

To  quote  from  the  standards  established  by  the  Secretary 
of  Agriculture  in  1906:  "A  flavoring  extract  is  a  solution 
in  ethyl  alcohol  of  the  proper  strength,  of  the  sapid  and 
odorous  principles  derived  from  an  aromatic  plant,  or  parts  of 
the  plant,  with  or  without  its  coloring  matter,  and  conforms 
in  name  to  the  plant  used  in  its  preparation."  Again  quoting : 
"  The  two  principal  flavors  are  vanilla  and  lemon,  it  being 
estimated  that  95  per  cent  of  the  flavoring  extracts  manu- 
factured are  of  these  two  varieties.  With  few  exceptions  the 
other  flavoring  extracts  are  artificial,  it  being  impossible  to 
manufacture  an  acceptable  extract  from  the  fruit  itself. 
Orange,  peppermint,  and  wintergreen  extracts  are  among 
the  exceptions  to  this  rule,  while  strawberry,  pineapple,  peach, 
and  some  others  are  artificial." 

Vanilla  extract  may  be  prepared  by  grinding  vanilla  beans 
in  a  meat  chopper  and  allowing  the  mass  to  soak  in  50  per  cent 
pure  grain  alcohol,  in  a  stoppered  bottle,  for  a  few  days.  This 
will  produce  a  delicately  flavored  extract  at  a  moderate  price. 

Chopped-up  orange  peeling,  or  lemon  peeling,  soaked  in 
95  per  cent  pure  grain  alcohol,  will  produce  satisfactory 
orange  or  lemon  extracts. 

Many  perfumes  may  be  made  by  chopping  the  material 
which  has  the  desired  odor  and  allowing  it  to  soak  in  95  per 
cent  alcohol  for  several  days. 

References :  — 

1.   Reprint  from  Yearbook  of  Department  of  Agriculture  for  1908 : 
The  Manufacture  of  Flavoring  Extracts. 

Experiment  80.  —  To  Make  Lemon  Extract. 

Apparatus :  Bottle  with  glass  stopper,  knife,  funnel. 
Materials :  Alcohol  95  per  cent,  lemon,  filter  paper. 


PLANT  FOOD  235 

a.  Carefully  peel  the  outside  of  the  lemon,  removing  only 
the  colored  part  and  cutting  off  as  little  of  the  white  part  as 
possible.  Put  the  cuttings  into  the  bottle  and  cover  with 
about  twice  their  volume  of  95  per  cent  alcohol.  Shake  the 
bottle  and  then  allow  it  to  stand  for  two  days.  Filter  into  a 
clean  dish  and  the  extract  is  ready  for  use.  See  reference 
for  full  directions  for  making  other  extracts. 

170.    PLANT  FOOD  — II 

This  subject  has  been  covered  in  the  consideration  of 
fertilizers,  humus,  irrigation,  drainage,  the  work  of  roots, 
and  the  work  of  leaves.  Thus  a  general  review  of  the  whole 
subject  can  be  taken  up  and  discussed. 

The  food  acquired  by  plants  is  not  all  utilized  immediately, 
but  may  be  stored,  as,  for  instance,  in  potatoes,  turnips, 
beets,  onions,  and  in  some  stalks.  The  food  is  used  for 
growth  as  well  as  for  fruit  and  seed  production.  If  the  amount 
of  food  is  reduced,  the  growth  of  fruit  is  increased,  but  at  the 
cost  of  the  plant  growth.  Reducing  the  growth  of  the  plant  also 
increases  the  yield  of  fruit.  Therefore  pruning  is  beneficial. 

Weeds,  through  a  long  process  of  evolution,  have  become 
adapted  to  living  better  than  any  beneficial  crop.  There- 
fore they  are  hard  to  kill,  but  their  destruction  is  necessary, 
since  they  remove  large  quantities  of  plant  food  and  water 
from  the  soil. 

References :  — 

1.  1407  :  8-11.  The  Storage  of  Food  in  the  Seed. 

2.  1503  f  95-96.  Food  Storage  in  Plants. 

3.  1601 : 147-153.  Osmosis  and  Diffusion  in  Plant  Feeding. 

4.  1605:68-71.  The  Manufacture  of  Food  Materials. 

5.  1702 :  242-246.  Movement    of    Plant    Juices  —  Chlorophyll 

and  Protoplasms. 

6.  Farmers'  Bulletin  No.  28.     Weeds  and  How  to  Kill  Them. 


236         INTRODUCTION  TO  GENERAL  SCIENCE 

7.  Farmers'    Bulletin    No.    44:    11-22.     Fertilizing    Material-- 

Plant Food. 

8.  Farmers'  Bulletin  No.  181.     Pruning, 
a.    1402:72-73.     The  Food  Material. 

6.  1402  :  74-84.  The  Making  of  Living  Matter. 

c.  1603  :  41-42.  Feeding  from  the  Air. 

d.  1603 :  31-33.  Feeding  from  the  Soil. 

e.  1611 :  81-90.  How  the  Plant  Uses  the  Food  it  Makes. 
/.  1612:44-51.  How  Plants  Feed. 

171.    THE  PROPAGATION  AND  BREEDING  OF  PLANTS 

Propagation  means  the  production  of  new  individuals. 
It  may  take  place  through  the  agency  of  roots,  cuttings, 
leaves,  buds,  grafts,  and  seeds. 

By  plant  breeding  is  meant  the  production  of  plants  having 
new  characteristics,  which  may  be  unlike  any  of  the  ancestors. 
Cross-pollination,  accomplished  and  regulated  by  man,  may 
produce  these  new  plants.  After  proper  selection  is  made  of 
the  plants  having  the  desired  characteristics,  and  these  plants 
are  bred  from,  there  can  gradually  be  produced  plants  having 
a  certain  feature,  to  any  desired  degree.  Nature  has  done 
the  same,  but  since  nature  necessarily  must  depend  to  such 
a  great  extent  upon  accidental  cross-pollination,  and  since 
many  accidents  may  happen  to  the  new  plants,  the  results 
have  not  been  as  rapid  as  when  the  work  has  been  carried  on 
by  man.  Also,  in  nature,  there  has  always  been  a  survival 
of  the  fittest;  there  is  a  continual  fight  for  existence,  and  the 
new  plant  may  not  be  as  well  adapted  to  maintain  its  existence 
as  some  of  the  older  forms.  With  man,  since  it  is  the  plant 
that  is  desired,  the  environment  is  adjusted  to  it,  and  the  new 
species  has  the  best  chance  of  living.  It  must  be  remembered, 
in  the  experiments  with  plants,  that  man  merely  directs  the 
course  that  nature  would  take  if  given  opportunity;  but  by 


PLANTS  — FORESTRY  237 

proper  direction  accidents  are  avoided  and  the  goal  is  reached 
much  more  quickly. 

References :  — 

1.  1407:500-513.  Plant  Breeding. 

2.  1503  : 116.  Budding  and  Grafting. 

3.  1605  :  36-55.  Propagation  of  Plants. 

4.  Farmers'  Bulletin  No.  157.     The  Propagation  of  Plants. 

5.  Farmers'  Bulletin  No.  409.     School  Lessons  on  Corn, 
a.    1402  :  20-22.         Propagation  of  Plants. 

6.  1404  : 19-29.  Propagation  by  Means  of  Roots  and  Stems. 

c.  1502 :  155-180.  Propagation. 

d.  1505 : 121-128.  Bud  Propagation. 

e.  1606 :  112-123.  Growth  of  Plants. 
/.  1606 : 132-140.  Propagation. 

g.    1608 : 148-156.     Propagation  of  Plants. 
h.   1609  :  314-315.     Modes  of  Reproduction. 
i.    1611 : 91-105.      How  Plants  are  Propagated. 

172.    PLANTS  —  FORESTRY 

While  the  effects  of  climate,  soil,  and  water  upon  plants  and 
all  vegetation  are  very  great,  yet  plants,  in  large  masses,  have 
a  reciprocal  effect  upon  these  very  factors  which  determine 
a  plant's  life.  Forestry,  or  a  study  of  the  needs  and  results 
of  forest  growth,  is  most  important.  The  forest  should  also 
be  considered  as  a  crop,  the  same  as  wheat,  barley,  or  any 
other  vegetable  growth  intended  for  the  use  of  mankind. 

Forests  regulate  the  flow  of  streams,  by  preventing  a  too 
rapid  run-off  of  rain  water.  For  the  same  reason,  they  cause 
more  water  to  enter  the  earth,  and  there  is  less  erosion  of  the 
good  land.  The  decaying  leaves  and  branches  produce 
humus,  and  thus  the  soil  is  enriched  where  forests  remain. 
More  than  this,  forests  prevent  high  winds,  moisten  the  air, 
and  actually  change  the  climate  of  a  locality  to  a  very  marked 


238          INTRODUCTION  TO  GENERAL   SCIENCE 

degree.     Fog  condenses  on  the  foliage  and  drips  to  the  ground, 
adding  a  little  to  the  streams. 

The  greatest  danger  to  forests  is  that  of  fire.  After  this 
come  destructive  lumbering,  trampling  and  browsing  by 
grazing  animals,  wind,  and  fungi. 

References :  — 

1.  1304:349-350.     Forest  Growing. 

2.  1407  :  490-492.     The  Forest  Region. 

3.  1503  :  116-117.     Forestry  and  the  Value  of  Trees. 

4.  1605  :  216-226.     The  Wood  Crop. 

5.  Farmers'  Bulletin  No.  173.      A  Primer   of    Forestry — The 

Forest. 

6.  Farmers'  Bulletin  No.  358.      A  Primer  of  Forestry  —  Prac- 

tical Forestry. 

7.  Farmers'  Bulletin  No.  134.       Tree  Planting  on  Rural  School 

Grounds. 

8.  Farmers'  Bulletin  No.  181.       Pruning. 

9.  Farmers'  Bulletin  No.  228.      Forest  Planting. 

10.  Farmers'  Bulletin  No.  423.     Forest  Nurseries  for  Schools. 

11.  Forest  Service,  Circular  130.     Forestry  in  the  Public  Schools. 

12.  Forest  Service,  Bulletin  36.     The  Woodsman's    Handbook. 

13.  Reprint  from  Yearbook  of  Department  of  Agriculture  for 

1903.     The  Relation  of  Forests  to  Stream  Flow. 

14.  Reprint  from  Yearbook  of  Department  of  Agriculture  for 

1905.     How  to  Grow  Young  Trees  for  Forest  Planting. 

a.  1402 :  222-223.     Rotation  of  Forests. 

b.  1502:365-391.     Forestry. 

c.  1606:3.  Forestry  Denned. 

173.    LOWER  FORMS  OF  PLANT  LIFE  —  BACTERIA,  MOLDS, 
AND  MILDEW 

Bacteria,  as  well  as  molds  and  mildew,  are  minute  plants, 
although  they  were  long  considered  as  having  animal  life. 
Their  greatest  peculiarity  is  the  method  by  which  they  are 


BACTERIA,   MOLDS,   AND   MILDEW  239 

propagated.  This  takes  place  by  means  of  spores  in  the  case 
of  molds,  mildews,  and  some  bacteria,  and  by  means  of 
division  with  most  bacteria. 

Bacteria  are  often  mentioned  only  as  disease  bacteria. 
We  must  not  get  the  idea  that  all  bacteria  are  bad,  for  such 
is  not  the  case.  There  are  only  about  twenty-two  species 
that  are  harmful  to  man,  while  there  are  several  thousands  of 
the  kind  which  aid  man  in  many  ways.  In  a  similar  manner 
the  white  corpuscles  of  the  body  are  helpers,  whose  function 
it  is  to  protect  us  from  the  inroads  of  the  harmful  bacteria. 

Other  bacteria  are  used  in  the  animal  system  to  assist  di- 
gestion, and  it  is  probable  that  digestion  would  be  of  longer 
duration,  if  it  were  not  for  these  agents.  Bacteria  enable 
plants  to  absorb  nitrogen  from  the  air;  they  cause  the  decay 
of  animal  matter,  as  well  as  vegetable  matter,  so  as  to  render 
proper  food  supplies  available  for  plants.  In  fact,  their  ad- 
vantages are  so  great  that  they  cannot  be  enumerated  in 
this  place.  Under  agriculture,  mention  has  been  made  of 
the  importance  of  the  nitrogen-fixing  bacteria,  as  well  as  the 
bacteria  of  decay. 

References :  — 

1.  1407:228-238.  Bacteria. 

2.  1501 :  382-390.  Bacteria  and  Disease. 

3.  1503:168-172.  Bacteria. 

4.  1601 : 124-130.  Nitrogen-fixing  Bacteria. 

5.  1605 :  97-99.  Life  in  the  Soil. 

6.  1901 : 1-12.  Introduction  to  the  Study  of  the  Lower 

Plants. 

7.  1901 : 12-39.  General  Nature  of  Molds. 

8.  1901 :  100-114.       General  Nature  of  Bacteria. 

9.  1901 : 124-131.       Dead  Food  Bacteria. 

10.  1901 :  203-211.       Disease  Bacteria. 

11.  1901 :  212-240.       Prevention  of  Contagious  Diseases. 


240         INTRODUCTION  TO  GENERAL  SCIENCE 

12.  Farmers'  Bulletin  No.  317:27-28.     "Starters"  for  Ripening 

Cream. 

13.  Farmers'  Bulletin  No.  348.     Bacteria  in  Milk. 

a.  1401 :  336-344.     Parasites. 

b.  1404:361-408.     Plants  which  cause  Fermentation,  De- 

cay, and  Disease. 

c.  1502  :  457-477.     Flowerless  Plants. 

d.  1611 : 183-226.     Friends  and  Foes  of  the  Plant. 

e.  1902  :  9-21.  General  Character  of  Bacteria. 

/.    1903  :  13-25.         General  Characteristics  of  Bacteria. 
g.    1903  :  168-174.     Nitrification  due  to  Bacteria. 
h.    1904:18-20.         Bacteria. 

174.  FERMENTATION  —  YEASTS 

Yeasts  are  small  plants  which  live  upon  starches  and 
sugars,  changing  them  into  alcohol  and  carbon  dioxide. 
The  highest  amount  of  alcohol  which  can  be  produced  by 
yeasts  is  about  14  per  cent,  as  yeasts  cannot  grow  if  there  is 
more  than  this  percentage  of  alcohol  present.  If  a  larger 
percentage  of  alcohol  is  desired,  as  in  whisky  or  brandy,  the 
fermented  material  must  be  distilled.  The  above  is  called 
alcoholic  fermentation. 

Yeasts  reproduce  themselves  by  budding;  that  is,  a  small 
bud  appears  upon  the  main  cell  and,  becoming  larger,  breaks 
off,  as  a  perfect  plant. 

There  is  another  kind  of  fermentation  which  is  called  acid 
fermentation.  Bacteria  are  the  cause  of  this,  and  examples 
of  bacterial  fermentation  are  the  souring  of  milk  and  the 
changing  of  cider,  or  wine,  to  vinegar. 

References :  — 

1.  1407:231-232.  Fermentation. 

2.  1501 :  41-48.  Fermentation  and  Alcohol. 

3.  1503 : 166-168  Yeasts  and  Fermentation. 


ALCOHOL  FOR  PURPOSES  OF  ENERGY  241 

4  1702:318-324.  Fermentation. 

5.  1703  : 194-195.  Fermentation. 

6.  1901:56-85.  Yeasts. 

7.  Farmers'  Bulletin  No.  175 :  6.     Causes  of  Fermentation. 

8.  Farmers'  Bulletin  No.  348.     Bacteria  in  Milk. 

a.  1405  :  232-234.  Yeast,  its  Food  and  Growth. 

6.  1502:465-466.  Yeasts. 

c.  1507  :  62-67.  Fermentation  and  Yeast. 

d.  1603:100-116.  Yeast    and    Bacteria  — the    Diseases    of 

Plants. 

e.  1704:260-261.     Fermentation. 
/.    1707:459-461.     Fermentation. 

g.    1708  :  406-410.     Fermentation  and  Life. 
h.    1711:291-293.     Fermentation. 
i.  1712:281-292.     Fermentation. 


175.    ALCOHOL  FOR  PURPOSES  OF  ENERGY 

The  United  States  Government  has  removed  the  internal 
revenue  tax  on  alcohol,  provided  it  is  used  for  purposes  of 
lighting,  heating,  cooking,  or  power.  Under  these  circum- 
stances the  alcohol  must  have  something  added  to  it  to  render 
it  unfit  for  drinking  or  as  a  medicine.  The  process  is  called 
denaturing,  and  the  alcohol  is  said  to  be  denatured.  For 
denaturing  purposes,  wood  alcohol,  benzine,  and  pyridin  are 
used. 

In  addition  to  the  removal  of  the  tax,  the  government  per- 
mits the  establishment  of  distilleries,  under  proper  supervision, 
and  the  manufacture  of  alcohol  may  be  carried  on  at  any 
place.  Alcohol  may  be  produced  from  many  of  the  waste 
products  of  the  farm,  and  thus  the  farmer  is  especially  bene- 
fited by  the  removal  of  the  tax  on  alcohol.  A  good  dis- 
tillery can  be  established  on  the  cooperative  basis,  and  can 
run  continually  in  every  small  community.  Any  vegetables, 


242          INTRODUCTION  TO  GENERAL  SCIENCE 

or  stalks  of  crops,  which  contain  starch  or  sugar,  are  sources 
of  alcohol. 

Alcohol  burns  with  a  nearly  colorless  flame,  without  soot; 
that  is,  there  is  complete  combustion.  See  Section  4,  Com- 
bustion. Therefore  the  flame  is  very  hot.  To  obtain  light, 
it  is  necessary  to  use  a  covering  for  the  flame,  which  is  ren- 
dered white-hot,  but  which  does  not  burn.  These  coverings 
are  made  of  rare  earths  and  are  called  incandescent  gas 
mantles. 

Gasoline  engines  can  be  adapted  to  the  use  of  alcohol,  and 
special  stoves  are  now  made  which  burn  alcohol  in  the  place 
of  gasoline.  Alcohol,  in  the  open  market,  is  more  expensive 
than  gasoline,  but  it  has  some  advantages  in  convenience 
and  safety.  Nevertheless,  since  alcohol  is  made  from  mate- 
rial which  would  otherwise  be  wasted,  there  is  a  decided  gain 
for  the  farmer  who  either  makes  his  own  alcohol,  or  who 
combines  with  his  neighbors  to  maintain  a  cooperative 
distillery. 

References :  — 

1.  1703 :  414-415.          Preparation  of  Ethyl  Alcohol. 

2.  Farmers'  Bulletin  No.  410.     Potato  Culls  as  a  Source  of  In- 

dustrial Alcohol. 

3.  Farmers'  Bulletin  No.  429.     Industrial  Alcohol. 

a.  1701:401-405.  Alcohol. 

b.  1704 :  209-214.  Alcohol  and  Distillation. 

c.  1705:155-156.  Alcohols. 

d.  1706:408-411.  Alcohols. 

e.  1707 : 471-472.  Alcohols. 
/.  1708 : 403-404.  Alcohols. 
g.  1709:381-384.  Alcohols. 
h.  1711:290-291.  Alcohols. 

i.    1712:273-276.     Alcohol.      Distillation    and    a    Test    for 
Alcohol. 


FUNGI,   RUSTS,   MUSHROOMS,   ETC.  243 

Experiment  81.  —  Sources  of  Alcohol. 

Apparatus :  Same  as  in  Experiment  17,  six  6"  X  8"  battery 
jars. 

Materials:  Grape  sugar,  molasses,  apples,  potatoes,  rice, 
beets,  starch,  grape  juice,  corn  stalks,  yeast  cakes. 

a.  Make  dilute  solutions  of  the  sugar  and  molasses  and 
pastes,  thinned  in  water,  called  mashes,  of  as  many  of  the  other 
materials  as  can  be  obtained.  Add  an  amount  of  yeast,  or 
yeast  sponge,  equal  to  about  10  per  cent  cf  the  mash,  in  each 
case.  Warm  gently  to  70°  F.,  and  allow  fermentation  to 
take  place  for  twenty-four  hours. 

6.  Distill  at  a  temperature  of  180°  F.,  and  burn  the  alcohol. 
Judging  from  your  own  experience,  which  material  produces 
the  most  alcohol? 


176.    LOWER    FORMS    OF    PLANT    LIFE  —  FUNGI,    RUSTS, 
MUSHROOMS,  ETC. 

Many  of  these  lower  forms  of  plant  life  are  not  supplied 
with  chlorophyll  and  cannot  produce  their  own  food.  Thus 
they  must  become  parasites  and  depend  upon  other  plants 
and  trees  for  their  support.  They  may  be  considered  as 
reducing  the  amount  of  organic  matter,  and  not  increasing 
it.  Saprophytes  are  useful  in  hastening  the  decay  of  dead 
vegetable  matter. 

References :  — 

1.    1407  :  227.  The  Fungi  and  What  They  Are. 

2     1503  :  159-166.  Fungi,  Parasites,  Saprophytes. 

3.  1605  :  250-254.  Fungus  Diseases  —  Scab,  Smut,  and  Rust. 

4.  Farmers'  Bulletin  No.  204.     Cultivation  of  Mushrooms. 

5.  Farmers'  Bulletin  No.  243.     Fungicides. 
a.   1401:274-277.     Fungi. 


244 


INTRODUCTION  TO  GENERAL  SCIENCE 


6.  1402: 
c.  1405: 
d.  1502: 

e.  1504; 
/.  1505: 
g.  1505: 
h.  1904: 

180-185. 
234-236. 
435-456. 

191-193. 
187-195. 
195-199. 
8-12. 

Fungi. 

Fungi  and  their  Mode  of  Life. 

Ferns,  Mosses,  Liverworts,  Lichens,  Algae, 

Mushrooms. 
The  Mushroom. 
Fungi. 

Lichens,  Liverworts,  and  Mosses. 
The  Relation  of  Fungi  to  Other  Plants. 

177.    PROTOZOA  AND  AMCEB^B 

The  protozoa  are  the  smallest  of  the  microscopic  animals, 
and  the  best  known  of  them  are  the  amcebce.  These  are 
about  one  one-hundredth  of  an  inch  in  diameter  and  consist, 
like  other  protozoa,  of  a  single  cell  composed  of  protoplasm. 

The  amoebae  move  from  place  to  place  by  means  of  flow- 
ing and  contracting.  They  feed  by  absorption ;  that  is,  they 
surround  their  food,  and  leave  the  undesired  particles  as  they 
move  on.  Water  is  also  absorbed  in  the  same  way.  Thus 
the  amcebse  grow  by  the  accumulation  of  food. 

Reproduction  is  effected  by  the  central  part,  or  nucleus, 
dividing  into  two  separate  parts;    the  whole  animal  then 
elongates  and  separates  between  the  two  nuclei.     Then  there 
are  two  amoebae. 
References :  — 

1.  1407:158-159. 

2.  1501:10-11. 

3.  1503:179-186. 

a.  1504:1-22.       , 

6.  1504:305. 

c.  1505:10-16. 

d.  1508:116-119. 
c.  1509:4-9. 

/.    1510:9-11. 


g.    1512:286-306. 


The  Amoeba. 
The  Amoeba. 
Protozoa. 
Amoeba. 

A  List  of  Protozoa. 
Protozoa  —  One-celled  Animals. 
Activities  of  One-celled  Animals. 
A  Simple  Type  of  Animal. 
Irritability,  Assimilation,  and   Reproduc- 
tion in  Amoeba. 
Protozoa. 


INSECTS  AND   THE  SMALLER  ANIMALS         245 

178.    INSECTS  AND  THE  SMALLER  ANIMALS 

Insects  are  air-breathing  animals  with  six  legs,  and  with 
their  bodies  divided  into  three  separate  parts.  Most  of  the 
insects  are  harmful  to  man,  since  they  either  live  upon  the 
bodies  of  animals,  or  vegetable  life,  which  are  valuable  to 
man.  Some  insects  consume  decaying  animal  and  vegetable 
matter,  and  enrich  the  soil  by  increasing  the  humus. 

Most  insects  pass  through  several  stages:  the  egg,  worm, 
cocoon,  or  a  dormant  state,  and  finally  the  mature  insect. 
The  worm  stage  is  the  one  in  which  the  most  damage  is  accom- 
plished. .  The  destruction  of  the  insect  in  the  dormant  state 
prevents  a  large  increase  of  its  kind,  because  it  is  the  adult 
which  lays  the  eggs  in  very  large  numbers. 

References :  — 


1. 

2. 
3. 

1304  :  359. 
1407  :  422-425. 
1503  :  227-255. 

Homes  of  Animals. 
Insects  Useful  to  Plants. 
Insects. 

4. 

1605  :  255-266. 

Insects 

and  their  Control. 

5. 

Farmers' 

Bulletin 

No.  127. 

Important  Insecticides. 

6. 

Farmers' 

Bulletin 

No.  145. 

Carbon  Bisulphide  as  an  Ini 

ticide 

, 

7. 

Farmers' 

Bulletin 

No.  155. 

How   Insects  Affect 

Health 

Rural  Districts. 

8. 

Farmers' 

Bulletin 

No.  196. 

Usefulness  of  the  Toad. 

a. 

1502: 

62-89. 

Insects 

of  the  Household. 

b. 

1505: 

63-85. 

Insects. 

c. 

1508: 

57-67. 

Some  Insects  Classified. 

d. 

1602: 

143-151. 

Animals  that  Destroy  Insects. 

e. 

1603: 

118-146. 

Orchard,  Garden,  and  Field  Insects. 

/. 

1604: 

60-89. 

Field  Laborers. 

g- 

1604: 

227-245. 

Guests, 

Welcome  and  Unwelcome, 

h. 

1604: 

300-312. 

Friends 

and  Foes. 

i. 

1604: 

313-336. 

Nature' 

s  Militia. 

j- 

1904: 

103-109. 

Disease 

Carried  by  Insects. 

in 


246          INTRODUCTION  TO  GENERAL  SCIENCE 


179.    THE  STINGS  OF  INSECTS 

The  pain  caused  by  stings  is  due  chiefly  to  formic  acid  or 
to  some  irritant  which  is  injected;  that  is,  the  effect  is  chem- 
ical. Ammonia,  since  it  neutralizes  an  acid,  is  good  to  allay 
the  pain. 

There  is  a  secondary  effect,  however,  for  which  the  insects 
are  not  responsible,  and  which  is  due  to  the  bacteria  or  pro- 
tozoa which  they  inject  at  the  time  they  sting.  Yellow  fever 
and  malaria  are  caused  only  by  the  bite  of  a  certain  kind  of 
mosquito  which  injects  protozoa.  Similarly,  the  "  sleeping 
sickness  "  is  due  to  another  species  of  protozoa  which  is 
injected  by  the  bite  of  a  fly,  similar  to  the  tsetse  fly. 

We  can  reduce  the  number  of  mosquitoes  and  finally  exter- 
minate them  from  a  given  locality  by  preventing  the  growth 
of  their  larvae,  commonly  called  "  wigglers."  This  can  be 
accomplished  by  pouring  crude  oil  upon  the  surface  of  the 
water  where  they  swarm. 

References :  — 

1.  1304:170.  Swamps  and  Malaria. 

2.  1501 :  154.  Insects'  Stings  and  Bites. 

3.  1503  :  185-186.          Mosquitoes  and  Flies  Transmit  Disease. 

4.  1901 :  214-220.          Malaria  and  Yellow  Fever  —  Mosquitoes. 

5.  Farmers'  Bulletin  No.  155.     How  Insects  Affect  Health  in 

Rural  Districts* 

a.    1308 :  143-145.     Man's  Enemies. 
6.    1505  :  160-161.     Mosquito  Fevers. 

c.  1506 :  269.  Malaria  from  Mosquito  Bites. 

d.  1507:132-135.     Malaria  and  Mosquitoes. 

e.  1509  :  189.  Malaria  and  Mosquitoes. 

/.    1904 :  103-109.     Malarial  Fever  and  Yellow  Fever. 
g.   1904:110-116.    Mosquitoes  and  their  Control. 


THE  INVERTEBRATES 


247 


180.    ANIMAL  LIFE  —  DISTRIBUTION 

The  distribution  of  animal  life  is  regulated,  or  governed, 
by  climate  and  the  physiography  of  the  land.  Some  animals 
are  fitted  to  live  in  warm,  and  others  in  cold,  climates.  Each 
class  is  thus  confined  to  its  own  locality.  Mountains,  oceans, 
large  bodies  of  water,  and  deserts,  prevent  the  distribution  of 
animals,  and  we  would  expect  to  find  distinct  species  in  iso- 
lated districts.  We  have  learned  from  travelers  that  this 
is  the  case. 


References :  — 

1.  1304:353-366. 

2.  1503:312-316. 

a.  1204 :  12-16. 

b.  1301 :  165-186. 

c.  1302:364-367. 

d.  1303:332-372. 

e.  1305:313-327. 
/.    1305:328-349. 
g.    1306:135-148. 

h.  1307:302-312. 

i.  1308:120-123. 

j.  1309:292-310. 

k.  1310:473-480. 

I.  1311:332-345. 

m.  1312 : 400-439. 

n.  1508:236-242, 


Distribution  of  Animals. 

Adaptation  of  Mammals. 

Geological  Control  of  Life. 

Distribution  of  Animal  Life  and  Plants. 

Animal  Geography. 

Distribution  of  Animals,  Plants,  and  Man. 

The  Various  Forms  of  Life. 

The  Distribution  of  Life. 

Geographic   Distribution  of  Animals  and 

Plants. 

The  Dispersal  of  Life. 
The  Organic  Environment. 
Distribution  of  Animal  Life. 
The  Environmental  Relations  of  Animals. 
Geographic  Conditions  of  Life. 
Geography  of  Plants  and  Animals. 
The  Distribution  of  Animals. 


181.    THE  INVERTEBRATES 

All  animals  come  under  two  general  heads :  Invertebrates 
and  Vertebrates.  The  latter  have  a  backbone  made  up  of 
sections  called  vertebrce,  while  the  former  either  have  no  bony 


248       INTRODUCTION  TO  GENERAL  SCIENCE 

structure  or  are  covered  with  some  kind  of  shell  or  horny 
substance. 

The  common  invertebrates  are  worms,  insects,  and  the 
crustaceans,  or  shellfish.  See  Section  178,  Insects  and 
Smaller  Animals.  Worms  are  very  beneficial  to  the  soil. 
See  Section  131,  Disintegration  due  to  Plant  and  Animal  Life. 

References :  — 

1.  1304 :  359.  Home  of  Invertebrates. 

2.  1503  :  191-193.  Sponges. 

3.  1503:208-214.  Worms. 

4.  1503:215-226.  Crustaceans. 

5.  1503:256-258.  Spiders. 

6.  1503:259-269.  The  Mollusks. 

a.   1504:304-306.  The    Chief    Divisions    of    the    Animal 

~  Kingdom. 

6.    1505  :  8-9.  Method  of  Classifying  Animals. 

c.  1505 : 17-21.  Sponges. 

d.  1505:42-50.  Worms. 

e.  1505:51-61.  Crustaceans. 

/.    1508 :  1-3.  Animals  Classified. 

g.    1508 :  243-254.     Animal  Relationships. 
h.    1512 :  284-285.     Classification  of  Animals. 

182.    ANIMAL  LIFE  —  FISHES,  ANIMALS,  AND  BIRDS 

It  is  quite  likely  that  the  first  living  beings  of  any  size  were 
water  animals,  although  not,  perhaps,  fishes. 

Some  of  these  water  animals  went  upon  the  land,  and  by 
persistent  habits,  through  untold  ages,  became  adapted  to 
life  on  land.  Others  developed  into  birds,  or  at  least  flying 
animals.  Those  species  which  became  best  adapted  to  any 
particular  kind  of  life  survived  and  produced  their  kind. 
The  others  died.  Thus,  starting  as  life  in  the  water,  all  the 
present  forms,  as  well  as  many  extinct  species,  have  developed. 


ANIMAL  LIFE— MAN  249 

References :  — 

1.  1304 :  359.  Homes  of  Animals. 

2.  1503:271-277.  Fishes. 

3.  1503:292-306.  Birds. 

4.  Farmers'  Bulletin  No.  54.     Some  Common  Birds. 

5.  Farmers'  Bulletin  No.  383.     How  to  Destroy  English  Spar- 

rows. 

a.  1502  :  305-307.  Our  Common  Birds. 

b.  1502  :  347-363.  Taming  and  Feeding  Birds. 

c.  1502  :  405-433.  Miscellaneous  Animals. 

d.  1504 : 141-147.  Creation  and  Evolution. 

e.  1505:109-121.  Fishes. 

/.    1505 : 126.  Animal  Life  Originated  in  the  Sea. 

g.    1505:150-165.  Birds. 

h.    1508 :  1-3.  Animals  Classified. 

i.    1508 : 169-177.  The  Structure  and  Activities  of  a  Fish. 

j.    1508:197-210.  Birds. 

k.   1512:154-167.  Fishes. 

I.    1512:208-221.  Birds. 


183.   ANIMAL  LIFE  —  MAN 

Man  is  the  most  highly  developed  animal  that  exists  on  the 
earth,  or  ever  has  existed.  In  man  we  have  the  highest  form 
of  brain,  and  the  mind  has  made  its  appearance.  The  one 
distinction  between  man  and  the  other  animals  is  that  man 
has  a  mind  and  can  direct  his  own  progress  and  advancement. 
With  other  animals  accident  plays  a  large  part,  but  is  nearly 
eliminated  in  man,  on  account  of  this  mind  and  the  possible 
education  which  he  may  receive.  Mental  development,  then, 
is  the  separating  feature  between  man  and  other  animals, 
as  far  as  the  physical  life  goes. 

See  Section  198,  The  Mind,  and  Section  201,  Man's  Place 
in  Nature.. 


250          INTRODUCTION  TO  GENERAL  SCIENCE 

References :  — 

1.  1205:443-449.  Man  and  his  History. 

2.  1304 :  367-392.  Man  and  Nature, 
a.    1206  :  438-443.  Advent  of  Man. 

6.  1302:383-392.  Geography  of  Man. 

c.  1305  :  326-327.  Development  Theory. 

d.  1306  :  407.  Man  and  Nature. 

e.  1307:335-351.  Man. 

/.  1308 :  126-142.  Human     Adaptation  —  Environment    of 

Influences. 

g.  1309:311-321.  Man. 

h.  1311 :  346-370.  The  Earth  and  Man. 

i.  1312 :  439-447.  Distribution  of  Mankind. 

j.  1313  :  229-231.  The  Historical  Distribution  of  Peoples. 

k.  1508:211-234.  Man's  Near  Relations. 

184.    THE  LIFE  PROCESSES 

The  simple  cell  is  the  foundation  of  all  life.  Thus  the  life 
of  a  plant,  or  an  animal,  is  composed  of  the  lives  of  an  almost 
infinite  number  of  cell  lives.  What  affects  the  cell  affects  the 
whole  plant  or  animal,  and  therefore  a  better  understanding 
of  the  elementary  life  is  necessary  if  we  are  to  comprehend 
the  life  processes  of  higher  plants  and  animals.  Just  as  the 
molecule  is  the  smallest  portion  of  matter  which  can  exist 
alone,  so  the  cell  is  the  smallest  portion  of  matter  which  can 

have  life.     The  cell  is  composed  of  protoplasm. 

• ' 
References :  — 

1.  1407  :  156-158.          The  Simplest  Living  Unit  a  Cell. 

2.  1501:9-20.  Cells. 

3.  1501 :  22-30.  Elements  of  the  Body. 

-  4.    1503  :  23-30.  Protoplasm  and  the  Cell. 

5.  1503:183-184.  The  Cell  a  Unit. 

6.  1702:243-244.  Protoplasm, 
a.    1406:11.  The  Cell. 


THE  BONES  251 

b.  1504 :  61-70.  The  Cell  the  Foundation  of  Life. 

c.  1505  :  10-16.  Protozoa  (One-celled  Animals). 

d.  1507  :  17-24.  Structure,  Life,  and  Work  of  Cells. 

e.  1509 : 1-9.  Plant  and  Animal  Life  in  the  Simplest 

Forms. 

/.    1510 :  9.  Meaning  and  Importance  of  the  Cell. 

g.    1511 :  5-6.  Cell  Structure. 

h.    1512:301.  The  Cell. 

i.    1704 :  281-286.     Physiological  Chemistry. 
j.    1708 :  409-411.     Chemistry  of  Life. 

185.    THE  BONES,  OR  FRAMEWORK 

Just  as  in  plants  the  stems  serve  to  hold  up  the  body,  so  in 
animals  some  stiff  structure  is  necessary.  The  complete 
framework  is  called  the  skeleton,  and  its  parts  are  called 
bones.  Bones  are  hollow  in  order  to  obtain  the  greatest 
strength  with  the  least  amount  of  material,  and  the  cavity 
is  used  to  supply  the  bones  with  nourishment. 

Most  animals  have  their  framework  covered  with  flesh,  but 
some  have  a  stiff  outside  covering  which  serves  the  same 
purpose  as  the  skeleton,  and  acts  as  a  protection  against 
enemies.  See  Section  181,  The  Invertebrates. 

In  order  to  allow  free  movements,  the  bones,  or  coverings, 
are  jointed,  being  held  together  by  cartilage.     These  places 
of  bending,  or  yielding,  are  called  joints. 
References :  — 

1.  1501:357-363.  The  Bones. 

2.  1501 :  364-369.  The  Joints. 

3.  1503  :  371-379.  Bones  and  Joints. 
a.    1505:29-38.             The  Skeleton. 

6.  1506  :  191-202.  Osseous  System  of  Bones. 

c.  1509:10-25.  The  Skeleton. 

d.  1510:103-111.  The  Skeleton  and  the  Muscles. 

e.  1511 : 11-43.  The  Osseous  System,  or  Skeleton. 


252         INTRODUCTION  TO  GENERAL  SCIENCE 


186.   THE  LEVER  AND  ITS  ADVANTAGE 

Any  body  which  moves  on  a  pivot,  and  has  one  part  farther 
away  from  the  pivot  than  another  part,  is  a  lever.  Any 
force  which  is  applied  to  the  end  farthest  from  the  pivot, 
will  cause  the  shorter  end  to  exert  a  greater  force.  The  rela- 
tion between  the  resulting  force  and  the  applied  force  is  the 
advantage  of  the  lever. 

The  most  common  example  of  the  lever,  which  has  a  large 
advantage,  is  the  crowbar.  If  a  man  desires  to  pry  up  a  rock, 
he  forces  the  bar  under  it  and  then  pushes  down  on  the  longer 
end.  Here  there  is  a  short  length  of  the  bar  under  the  rock; 
the  bar  is  pivoted  on  the  ground  near  the  rock,  and  the  longer 
portion  of  the  bar,  upon  which  the  force  is  applied,  extends 
upward.  If  the  part  of  the  bar  which  is  beyond  its  resting 
point,  or  pivot,  is  one  tenth  of  the  longer  end,  a  man  who 
weighs  one  hundred  and  fifty  pounds  can  move  a  rock  weigh- 
ing ten  times  his  own  weight,  or  fifteen  hundred  pounds. 
The  advantage  of  the  lever,  in  this  case,  is  ten. 

Sometimes  the  force  is  applied  to  the  shorter  end  of  the  lever 
in  order  to  obtain  greater  velocity  at  the  other  end.  This 
is  obtained  at  the  expense  of  force ;  that  is,  the  force  applied 
must  be  greater  than  the  force  which  is  obtained  at  the  longer 
end.  The  force  multiplied  by  the  numerical  measure  of  the 
distance  through  which  it  acts  is  equal  for  both  ends  of  the 
lever.  The  bones  and  joints  of  animals  form  levers  of 
this  style,  and  since  the  muscle  acts  on  the  shorter  arm  of 
the  lever,  there  is  a  mechanical  disadvantage.  That  is,  the 
muscle  must  pull  much  harder  than  the  force  which  is  being 
overcome  when  the  animal  moves.  Thus,  in  holding  at  arm's 
length  a  weight  of  twenty  pounds,  the  muscle  of  the  arm  is 


THE  LEVER  253 

obliged    to    contract    with    a    force  of    over  two  hundred 
pounds. 

The  lever  is  the  fundamental  basis  for  many  machines,  and 
the  moving  pulley  and  the  gear  are  only  special  forms  of 
levers.  The  human  and  other  skeletons  contain  many 
examples  of  the  lever. 

References:  — 

1.   1803:151-154.  The  Lever. 

a.  1509 :  53-55.  Kinds  of  Levers. 

b.  1801 :  83-85.  The  Lever,  its  Advantage  and  Use. 

c.  1802  : 146.  The  Lever. 

d.  1804 :  102-104.  Experiments  with  the  Lever. 

e.  1805 :  84-88.  The  Lever  and  its  Law. 

/.  1806 :  65-68.  The  Lever,  Straight  and  Circular. 

g.  1807  :  123-127.  The  Lever  and  its  Applications. 

h.  1808 :  88-93.  The  Lever  —  Straight,  Bent,  Compound. 

i.  1809  :  81-83.  The  Lever  and  its  Applications. 

j.  1810 :  2-7.  Levers. 

k.  1811 :  355-356.  The  Lever. 

Experiment  82.  —  The  Lever. 

Apparatus:  A  stick  36"  X  1"  X  J",  with  holes  bored  every 
inch  through  the  middle  of  the  flat  side,  ring  stand,  nails  to 
fit  holes,  3  double  hooks  of  wire  to  hook  over  both  ends  of  a 
nail  when  it  is  pushed  through  a  hole  in  the  stick,  having  a 
third  hook  opposite  the  double  part,  12  iron  balls  all  of  the 
same  size,  with  hooks  on  opposite  sides. 

a.  Push  a  nail  through  the  middle  hole,  and  support  the 
stick,  by  one  hook,  on  a  ring  stand.  Push  a  nail  through  the 
first  hole  to  the  left  and  another  nail  through  the  second  hole 
to  the  right.  How  many  more  balls  can  be  hung  on  one  side 
than  on  the  other  ?  On  which  side  is  the  greater  weight  ? 
Double  the  number  of  balls  on  one  side.  How  many  times 
the  original  number  can  now  be  supported  on  the  other  side  ? 


254        INTRODUCTION  TO  GENERAL  SCIENCE 

b.  Repeat  (a),  but  go  out  to  the  fifth  hole  on  one  side. 
Make  a  table  of  your  results  in  (a)  and  (6). 

c.  Try  some  original  experiment  with  this  lever,  and  write 
out  what  you  did  and  the  results  which  you  obtained. 

d.  Describe  a  method  of  weighing  ten  pounds  with  a  one- 
pound  weight  and  a  stick. 


187.    THE  MUSCLES 

Movement,  even  with  the  joints,  would  be  impossible,  if  it 
were  not  for  the  muscles,  which,  by  contracting  or  relaxing, 
shorten  and  lengthen,  thus  moving  the  parts  to  which  they 
are  attached.  Muscles  form  the  flesh,  or  meat,  of  animals, 
and  are  the  parts  which  are  eaten  as  animal  food.  Exercise 
hardens  the  muscles,  and  it  can  be  readily  seen  that  animals 
intended  for  the  food  of  man  should  not  be  allowed  to  exercise 
more  than  enough  to  maintain  their  health.  All  muscles 
work  at  a  mechanical  disadvantage.  See  preceding  section. 

A  uniform  development  of  the  muscles  of  our  bodies  is 
desirable,  and  this  can  only  be  secured  by  regular  and  special 
exercises.  A  person's  usual  employment  generally  develops 
a  certain  set  of  muscles,  and  unless  he  artificially  exercises 
the  other  muscles,  he  is  liable  to  become  deformed. 

References :  — 

1.  1501 :  371-379.          Muscles  and  Exercise. 

2.  1503:362-367.  The  Muscles. 

a.  1505:39-50.  The  Muscles. 

b.  1506 :  203-212.  The  Muscular  System. 

c.  1507:273-288.  Muscles. 

d.  1509  :  40-49.  Muscles  and  Tendons. 

e.  1510:99-102.  The  Muscles. 

/.    1511:47-72.         The  Muscular  System. 


RESPIRATION  255 

188.  THE  BLOOD 

The  blood  serves  as  a  carrier  of  food  and  oxygen  to  all  parts 
of  the  body.  It  is  the  builder  and  also  the  cleanser  of  the 
system.  In  the  digestive  organs  the  blood  takes  up  the  newly 
prepared  body  food  and  distributes  it  to  all  the  living  cells, 
in  every  part  of  the  body.  The  oxygen,  which  the  blood 
receives  in  the  lungs,  is  also  carried  to  every  cell,  by  means 
of  red  corpuscles,  where  it  burns  up  the  waste  material,  chang- 
ing it  into  such  a  shape  that  it  can  be  carried  to  the  lungs, 
where  it  is  exhaled  as  carbon  dioxide  and  decayed  animal 
matter,  and  to  the  perspiratory  glands,  where  it  is  carried  off 
mechanically.  The  kidneys  absorb  other  waste  from  the 
blood. 

The  white  corpuscles  serve  as  protective  agents,  destroying 
bacteria  which  enter  through  a  broken  skin. 

References :  — 

1.  1501 :  156-161.  The  Blood. 

2.  1501 :  161-169.  The  Heart. 

3.  1503:344-349.  The  Blood. 

4.  1503  :  392-394.  The  Human  Kidney. 
a.    1505  :  52-69.  The  Circulation. 

6.  1506 :  106-113.  The  Blood  and  its  Uses. 

c.  1507  :  126-127.  White  Blood  Corpuscles. 

d.  1509  :  135-152.  The  Circulation  of  the  Blood. 

e.  1509  :  196-199.  The  Removal  of  Waste  Products. 
/.  1510  :  67-86.  Circulation. 

g.    1511 :  75-105.       The  Blood  and  its  Circulation. 

189.  •  RESPIRATION 

The  material  in  the  blood  must  receive  a  sufficient  supply  of 
oxygen  in  order  that  the  waste  material  may  be  consumed. 
The  lungs  supply  this  need,  and  man  inhales  about  thirty^ 


256          INTRODUCTION  TO  GENERAL  SCIENCE 

cubic  inches  of  air,  eighteen  times  a  minute,  from  which  part 
of  the  oxygen  is  absorbed.  All  living  beings,  including  the 
microscopic  forms,  require  oxygen.  Even  fishes  absorb  it 
from  the  air  which  is  dissolved  in  the  water,  and  will  die  in 
water  from  which  the  air  has  been  removed.  Plants  also 
breathe,  but  this  absorption  of  oxygen  must  not  be  confused 
with  the  work  c-f  the  leaves. 

While  we  breathe  only  about  thirty  cubic  inches  per  breath, 
this  does  not  nearly  represent  the  capacity  of  the  lungs,  which 
is  about  three  hundred  and  thirty  cubic  inches.  It  is  easy  to 
see,  then,  that  in  ordinary  breathing  we  do  not  supply  our 
lungs  with  fresh  air,  but  merely  dilute  the  vitiated  air  that  is 
already  there.  If  we  wish  to  be  in  a  healthy  condition,  we 
must  realize,  then,  that  at  several  periods  during  the  day  we 
should  make  an  effort  to  exhale  all  the  air  possible  from  our 
lungs  and  then  to  take  a  very  deep  breath,  repeating  this 
four  or  five  times.  The  effect  on  the  health  of  a  person  who 
will  do  this  every  few  hours,  out  in  the  fresh  air,  is  quite 
marvelous.  Part  of  the  advantage  of  vigorous  exercise  is 
due  to  the  fact  that  we  must  breathe  more  deeply  when 
exercising  than  we  do  ordinarily.  Although  some  of  us  are 
not  strong  enough  to  take  violent  exercise,  yet  we  can  all 
breathe  deeply  at  some  period  during  the  day. 

Human  beings  breathe  in  two  ways.  Women  breathe 
from  the  chest,  men  from  the  abdomen.  It  is  probably  true 
that  both  methods  are  wrong.  The  woman  exercises  the 
upper  part  of  her  lungs,  and  the  man  the  lower  part.  It  does 
not  tend  to  produce  even  development,  and  both  ways  leave 
part  of  the  lungs  unaffected.  Both  ways  tend  to  produce 
disease  of  the  lungs,  since  it  is  only  by  the  vigorous  use  of  all 
parts  of  our  body  that  we  can  maintain  our  health.  Nature 
always  takes  away  from  us  what  we  do  not  use.  The  proper 


DANGERS  OF  VITIATED  AIR  257 

way  to  breathe  is  to  have  both  the  chest  and  the  abdomen 
partly  inflated  when  each  breath  is  taken. 

References :  — 

1.  1407 : 110-112.          Respiration  in  Plants. 

2.  1501:192-204.          The  Lungs. 

3.  1503:380-390.          Respiration. 

a.  1404 : 194-195.  The  Breathing  of  Plants. 

b.  1505  :  72-88.  Respiration  and  Ventilation. 

c.  1506 :  138-149.  The  Lungs  and  Breathing. 

d.  1507 : 190-210.  The  Mechanism  and  Chemistry  of  Res- 

piration. 

e.  1509 :  165-178.     Respiration. 
/.    1510 :  23-44.         Respiration. 

g.    1511  :  107-121.     The  Respiratory  Organs. 

190.    DANGERS  OF  VITIATED  AIR 

The  air  of  an  insufficiently  ventilated  room  contains,  after 
occupancy,  a  considerable  quantity  of  carbon  dioxide,  par- 
ticles of  animal  tissue  which  have  been  expelled  from  the  lungs, 
disease  germs,  and  unpleasant  if  not  dangerous  odors  from 
perspiration.  The  odor  of  the  air  in  a  room  is  a  good  index  of 
its  impurity,  although  the  odor,  in  itself,  may  be  harmless. 
A  test  for  the  amount  of  carbon  dioxide  present  likewise  indi- 
cates the  degree  of  vitiation,  six  parts  in  ten  thousand  being 
as  much  as  can  be  safely  endured,  although  this  amount  of 
carbon  dioxide  alone  is  harmless. 

Vitiated  air  tends  to  produce  a  poor  appetite,  weakens  the 
constitution,  and  may  lead  to  consumption.  The  effects  of 
bad  air  are  slow  in  their  results  and  too  often  are  not  recog- 
nized as  due  to  lack  of  sufficient  ventilation.  Many  a  vaca- 
tion trip  owes  all  its  beneficial  results  to  the  fact  that  fresh 
air  was  unlimited.  Consumption  is  being  cured  by  plenty  of 

B 


258         INTRODUCTION  TO  GENERAL  SCIENCE 

fresh  air  by  night  as  well  as  by  day.     See  Section  19,  Ven- 
tilation and  Heating  of  Buildings. 

References :  — 

1.  1501 :  223-230.  Dangers  of  Impure  Air. 

2.  1503  :  387-388.  Need  of  Ventilation. 

3.  1702:66-71.  Air  and  Ventilation. 

4.  1710 :  16-22.  Substances  in  the  Air. 

5.  1710 :  40.  Dangers  from  Air  Vitiation. 
6.    1901 :  230-234.     The  Air  and  Disease. 

a.  1505 :  80-86.  Hygienic  Habits  of  Breathing. 

6.  1506 :  153-156.  Impurities  in  the  Air. 

c.  1507 :  206-209.  Evils  of  Indoor  Life. 

d.  1509  :  182-184.  Effects  of  Respired  Air. 

e.  1509  :  189-192.  Dust  and  Disease. 

/.  1510 :  40-42.  Hygiene  of  Respiration. 

g.  1511 : 128-129.  Object  and  Need  of  Ventilation. 

h.  1904 :  63-67.  Care  of  Consumptives. 

i.  1905 : 33-38.  Impurities  in  Air,  their  Effects  and  Tests. 

Experiment  83.*  —  Test  for  Bad  Air. 

Apparatus:  A  twenty-ounce  glass  stoppered  bottle,  glass 
measure  graduated  in  cubic  centimeters,  medicine  dropper 
graduated  to  hold  one  third  of  a  cubic  centimeter. 

Materials :  Limewater  solution  (pure  water  left  in  contact 
with  slaked  lime  until  saturated.  Dilute  the  clear  decanted 
liquid  with  99  times  its  own  volume),  phenolphthalein  solu- 
tion (dissolve  one  part  of  phenolphthalein  in  500  times  its 
own  weight  of  50  per  cent  alcohol). 

a.  Fill  bottle  with  pure  water,  and  empty  it  in  the  place 
where  the  air  is  to  be  tested.  This  will  insure  the  bottle  being 
filled  entirely  with  the  air  of  the  room.  Add  10  c.c.  of  lime- 
water  solution  and  one-third  c.c.  of  phenolphthalein  solution, 

*  After  Dr.  J.  B.  Cohen,  modified. 


FOOD  AND  NUTRITION  259 

stopper,  and  shake.  If  the  red  color  disappears  in  three 
minutes  or  less,  the  air  is  unfit  to  breathe. 

The  following  table  is  taken  from  book  No.  1905. 

"  The  percentage  of  carbon  dioxide  may  be  estimated  from 
the  time  which  it  takes  to  decolorize  the  phenolphthalein  as 
follows :  — 

TIME  PER  CENT  VOLUME 

Minutes  Carbon  Dioxide 

1J  1618 

If 1318 

1| .1279 

3i 07716 

4i 05142 

5 0434 

7| 0351" 

6.   See  Experiment  48  for  another  test  for  carbon  dioxide. 


191.    FOOD  AND  NUTRITION 

We  learned,  in  connection  with  plants,  that  food  was  nec- 
essary to  promote  growth,  and  to  supply  the  wastes  which  are 
going  on  all  the  time.  With  animals,  food  is  even  more  nec- 
essary, for,  on  account  of  their  great  activity,  they  require  it  in 
much  larger  quantities. 

Food  serves  three  purposes:  to  supply  energy,  fat,  and 
muscle-forming  materials.  The  warmth  of  the  body  is  pro- 
duced by  slow  oxidation  of  the  carbohydrates  contained  in 
some  foods,  as  well  as  by  fats.  Fats,  in  the  body,  serve  as 
storehouses  of  food  which  can  be  utilized  if  the  food  supply  is 
lacking.  Proteids  supply  material  for  the  production  of  new 
cells.  Other  things  being  equal,  the  moderately  fat  person 
has  a  better  chance  to  survive  a  period  of  starvation  than  a 
thin  person. 


260         INTRODUCTION  TO  GENERAL  SCIENCE 

The  amount  of  food  consumed  does  not  determine  whether 
a  person  is  to  receive  great  or  little  good  from  it.  The  diges- 
tion and  assimilation  of  the  food  are  what  count.  Many  thin 
persons  have  enormous  appetites,  while  some  fat  persons  eat 
but  little. 

References :  — 

1.  1304 :  370-371.  Food  Supply. 

2.  1501 : 131-134.  Quantity  of  Food  Required. 

3.  1503:20-22.  Foods. 

4.  1503:317-324.  Foods. 

5.  1702 :  374-392.  Rational  Feeding  of  Men. 

6.  1710:117-125.  Use  of  Foods. 

7.  Farmers'  Bulletin  No.  142.     Principles  of  Nutrition  and  Nu- 

tritive Value  of  Food. 

a.  1505  :  91-93.  The  Four  Kinds  of  Nutrients. 

6.  1506 :  35-45.  Food  and  its  Uses. 

c.  1507 :  37-61.  Foods  and  Food  Habit. 

d.  1509  :  65-72.  Selection  and  Preparation  of  Foods. 

e.  1510:51.  The  Five  Food  Substances. 
/.  1511:143-192.  Nutrition. 

g.    1708 :  410-411.     Food  of  Man. 

192.    DIGESTION 

When  we  eat  food,  it  may  or  may  not  do  us  good,  according 
to  our  ability  to  digest  and  to  absorb  the  useful  parts  of  it. 
Digestion  and  absorption  are  entirely  different.  Absorption 
is  the  taking  up,  by  the  blood,  from  the  walls  of  the  stomach 
and  intestines,  the  food  material  which  can  be  used  by  the 
system.  Digestion  is  merely  the  rendering  soluble  of  the  en- 
tire mass  of  food  which  is  taken  into  the  stomach;  that  is,  the 
food  must  be  turned  into  a  more  or  less  liquid  condition. 

The  stomach  supplies  the  gastric  juice,  which  contains  .2 
per  cent  of  an  acid  called  hydrochloric,  and  two  ferments  called 


DIGESTION  261 

pepsin  and  renin.  The  latter  acts  by  coagulating  milk;  the 
former  softens  proteids  and  tends  to  change  them  into  a  kind 
of  fluid  called  peptone. 

The  action  of  the  dilute  hydrochloric  acid  is  to  neutralize 
the  alkali  which  is  always  found  in  food,  and  to  kill  bacteria 
which  would  cause  fermentation.  The  acid  can  also  begin 
the  changing  of  proteids,  while  pepsin  cannot  act  except 
in  the  presence  of  hydrochloric  acid.  After  digestion  in  the 
stomach  the  food  is  in  a  liquid  form  called  chyme.  Starches 
and  sugars  are  digested  in  the  intestines,  and  it  is  here  that 
most  of  the  absorption  of  food  takes  place.' 

References :  — 

1.  1501 :  51-63.  Digestion  of  Food  in  the  Mouth. 

2.  1501 :  66-70.  Digestion  of  Food  in  the  Stomach. 

3.  1501 :  79-86.  Digestion  of  Food  in  the  Intestines. 

4.  1501 :  89-96.  Absorption  and  Assimilation. 

5.  1503  :  330-343.  Digestion  and  Absorption. 

6.  1702  :  325-343.  Digestion  and  Nutrition. 

a.  1505  :  89-116.      Food  and  Digestion. 

b.  1506  :  76-88.         The  Digestive  System. 

c.  1507 :  74-87.         Digestion  of  Food  ;  the  Mouth  and  the 

Throat. 

d.  1507 : 112-121.     The  Absorption  of  Food. 

e.  1509:96-114.       Digestion. 
/.    1510:55-58.         Digestion. 
g.    1511 :  193-224.     Digestion. 

Experiment  84.  —  Digestion  of  a  Proteid. 

Apparatus :  Test  tubes  6"  x  f",  beaker  200  c.c.,  ring  stand, 
asbestos  mat,  burner,  thermometer. 

Materials:  Pepsin,  hydrochloric  acid,  10  per  cent,  cooked 
white  of  an  egg. 

a.  Chop  finely  a  small  piece  of  the  egg  and  place  it  in  a  test 
tube  with  water.  Can  you  see  any  change  after  two  hours  ? 


262          INTRODUCTION  TO  GENERAL  SCIENCE 

b.  Put  some  more  chopped  egg  in  another  test  tube  and 
cover  with  half  water  and  half  10  per  cent  hydrochloric  acid. 
This  gives  a  5  per  cent  solution.     What  is  the  result  after  two 
hours  ? 

c.  Repeat  (a),  adding  2  per  cent  pepsin  to  the  water. 

d.  Repeat,  using  2  per  cent  pepsin  and  5  per  cent  acid. 

e.  Put  the  four  tubes  (a),  (b),  (c),  and  (d)  in  water  main- 
tained at  a  temperature  of  98°  F.;  and  note  the  result  in  two 
or  three  hours. 

193.    FOOD  —  VEGETABLE  FOOD 

The  food  of  man  falls  naturally  into  two  general  divisions : 
that  which  is  obtained  from  plants,  and  that  from  animals. 
Since  man  is  an  animal,  it  is  doubtful  if  his  body  can  work  to 
the  best  advantage  without  some  animal  food,  either  meat, 
or  milk  and  its  products,  as  well  as  eggs.  Vegetable  food  is 
lacking  in  some  of  the  constituents  which  form  part  of  the 
animal  body,  and  those  constituents  must  be  supplied. 

Vegetable  food  contains  a  large  amount  of  water,  which  is 
beneficial,  while  fruits  have  a  very  salutary  dietetic  effect, 
far  exceeding  their  food  value.     People,  as  a  rule,  do  not  eat 
enough  vegetables  and  fruits. 
References :  — 

1.  1407 :  514-523.     Food  Products  for  Human  Use. 

2.  1501:120-129.    Vegetable  Food. 

3.  1702 :  397-398.     Composition  of  Vegetable  Foods. 

4.  1710 :  212-222.     The  Composition  and  Food  Value  of  Fruits. 

5.  1901 :  86-99.         Bread  Raising ;  Fermented  Liquors. 

6.  Farmers'  Bulletin  No.  93.     Sugar  as  Food. 

7.  Farmers'  Bulletin  No.  105 :  19-22.     Cereal  Breakfast  Foods. 

8.  Farmers'  Bulletin  No.  389.     Bread  and  Bread  Making. 

9.  Farmers'  Bulletin  No.  121.     Peas,  Beans,  and  Other  Legumes 

as  Food. 


FOOD  — ANIMAL  FOOD  263 

10.  Farmers'  Bulletin  No.  249.      Cereal  Breakfast  Foods. 

11.  Farmers'  Bulletin  No.  256.     Preparation  of  Vegetables  for 

the  Table. 

12.  Farmers'  Bulletin  No.  293.     Use  of  Fruit  as  Food. 

13.  Farmers'  Bulletin  No.  295.     Potatoes  and  Other  Root  Crops 

as  Food. 

14.  Farmers'  Bulletin  No.  298.     Food  Value  of  Corn. 

15.  Farmers'  Bulletin  No.  332.     Nuts  and  their  Uses  as  Food. 

Experiment  85.  —  The  Amount  of  Water  in  Vegetables. 

Apparatus :  Ring  stand,  asbestos  mat,  burner,  evaporating 
dish,  balances,  set  of  weights,  hard  glass  tube. 

Materials:   Potato,  apple. 

a.  Cut  the  potato  or  apple  into  small  cubes,  and  weigh  out 
20  grams  in  an  evaporating  dish.  Warm  over  the  burner,  at 
first  slowly  and  then  more  vigorously,  until  the  material  begins 
to  char.  Then  weigh  again.  How  much  water  was  driven 
off  from  the  20  grams  ?  Divide  this  by  twenty  and  multiply 
by  one  hundred  and  obtain  the  percentage  of  water.  In  100 
pounds  of  potatoes,  how  much  water  is  there  ? 

6.  Put  the  dried  pieces  in  a  hard  glass  tube,  and  heat 
strongly.  When  smoke  comes  from  the  mouth  of  the  tube, 
it  may  be  lighted.  After  all  smoke  has  ceased  being  evolved, 
weigh  the  residue.  What  is  it  ?  See  Experiment  18. 

194.    FOOD  —  ANIMAL  FOOD 

While  the  flesh  and  some  interior  organs  of  animals  are 
used  as  food  for  man,  and,  although  some  animal  food  is  nec- 
essary for  man,  it  is  no  doubt  true  that  too  much  meat  is 
eaten.  Meat  is  a  decidedly  rich  and  compact  food,  and  man 
needs  but  little  to  supply  his  wants.  Meat  is  expensive,  and 
thus  a  proper  study  of  the  real  necessities  for  food  could  cause 
a  person  to  have  better  health  and  to  live  less  expensively. 


264         INTRODUCTION  TO  GENERAL  SCIENCE 

It  does  not  always  follow  that  the  most  agreeable  food  is 
the  best  for  the  system.  Some  of  the  cheaper  and  tougher 
portions  of  meat  contain  more  available  food  than  the  better 
and  more  expensive  parts.  However,  we  must  remember 
that  a  man  is  not  a  machine,  and  that  well-being  and  hap- 
piness are  just  as  necessary  as  the  proper  food. 

References :  — 

1.  1501 :  107-118.     Animal  Food. 

2.  1605  :  281-282.     Importance  of  Animal  Food.   • 

3.  1702  :  393-396.     Composition  of  Animal  Foods. 

4.  1710 :  228-256.     Animal  Foods. 

5.  Farmers'  Bulletin  No.  34.     Meats,  Composition  and  Cook- 

ing. 

6.  Farmers'  Bulletin  No.  85.  Fish  as  Food. 

7.  Farmers'  Bulletin  No.  128.  Eggs  and  their  Uses  as  Food. 

8.  Farmers'  Bulletin  No.  182.  Poultry  as  Food. 

9.  Farmers'  Bulletin  No.  183  Meat  on  the  Farm. 

10.  Farmers'  Bulletin  No.  363.     The  Use  of  Milk  as  Food. 

11.  Office  of  Experiment  Stations,  Bulletin   No.  162.     The  In- 

fluence of  Cooking  upon  the  Nutritive  Value  of  Meat. 

12.  Bureau  of  Animal  Industry,  Circular  56.     Facts  concerning 

the  History,  etc.,  of  Butter. 

195.    FOOD  ANALYSIS 

Under  the  heading  of  food  analysis  are  two  branches  : 
the  tests  for  the  ingredients  of  which  the  food  is  composed, 
that  is,  fats,  proteids,  and  carbohydrates ;  and  the  tests  for 
adulterants  and  preservatives. 

The  common  nutrients  are  the  fats,  proteids,  and  carbohy- 
drates. Starch  and  sugar  are  examples  of  the  last.  These 
three  kinds  of  material  exist  together  in  many  of  our  foods, 
although  any  one  of  them  may  be  practically  alone  in  some 
foods.  It  is  of  value  to  us  to  know  what  our  food  contains,  in 


FOOD  ANALYSIS  265 

order  that  we  may  consume  a  sufficient  quantity  of  the  right 
kinds. 

There  is  always  a  temptation  to  adulterate  food  offered  for 
sale,  as  well  as  to  color  it  artificially,  and  also  to  add  preserva- 
tives which  may  affect  the  health  of  the  consumer.  Nearly 
all  of  the  foreign  matter  can  be  detected  by  the  proper  test, 
and  the  tests  for  the  common  substances  are  given  in  Experi- 
ment 87. 

References :  — 

1.  1501:111-112.  Adulteration  of  Milk. 

2.  1503  :  21-22.  Tests  for  Nutrients. 

3.  1503  :  323-324.  Adulterations  in  Food. 

4.  1605  :  282-287.  Compositions  of  Food  —  the"  Use  of  Each 

Part. 

5.  1710:123-125.       Kinds  of  Foods. 

6.  1710  :  242-250.       Milk  Analysis  and  Tests. 

7.  1710 :  304-307.       Tests  for  Preservatives  and  Coloring  Matter 

in  Foods. 

8.  Farmers'  Bulletin  No.  131.     Tests  on  Butter. 

9.  Office  of  Experiment  Stations,  Bulletin  No.  162.     Studies  on 

Meat. 

a.  1505  :  93-94.  Adulteration  of  Food. 

b.  1506  :  42-43.  Adulteration  of  Food. 

c.  1507  :  46-48.  Composition  of  Common  Foods. 

d.  1509 :  83-86.  Tests  on  Food. 

Experiment  86.  —  Composition  of  Food. 

Apparatus :  Ring  stand,  burner,  asbestos  mat,  evaporating 
dish,  test  tubes,  beaker,  100  c.c.,  flask  150  c.c.,  funnel,  filter 
paper. 

Materials :  Iodine  solution  (make  a  10  per  cent  solution  of 
potassium  iodide,  dissolve  as  much  iodine  in  it  as  possible,  and 
then  dilute  with  nine  times  as  much  water).  Fehling's  so- 
lution (make  three  stock  solutions:  (1)  copper  sulphate, 


266         INTRODUCTION  TO  GENERAL  SCIENCE 

9  g.  in  25  c.c.  water;  (2)  sodium  hydrate,  30  g.  in  250  c.c. 
water;  (3)  Rochelle  salts,  43  g.  in  250  c.c.  water.  To  use, 
take  equal  parts  of  (1),  (2),  and  (3),  and  two  parts  water), 
litmus  paper,  concentrated  nitric  acid,  ammonium  hydrate, 
benzine  or  ether,  powdered  chalk,  potato,  concentrated  sul- 
phuric acid,  cotton  cloth  for  strainer. 

a.  Grind  or  slice  material  to  be  tested,  and  let  stand  in  a 
little  water.  Add  a  few  drops  of  iodine  solution.  A  blue 
color  indicates  starch.  If  the  mixture  turns  black,  add  more 
water  and  the  blue  color  will  appear. 

6.  Bring  from  home  a  little  of  rice,  wheat,  beans,  peanuts, 
and  apple,  and  test  each  for  starch. 

c.  Make  some  potato  pulp,  mix  it  with  water,  and  strain  it 
through  a  cloth.     Let  liquid  stand  until  the  solid  settles,  then 
pour  off  clear  liquid  and  dry  the  residue  by  gentle  heat.     This 
is  starch.     Prove  it  by  testing  a  little.     Also  taste  a  little  and 
describe  its  taste.     Add  1  c.c.  concentrated  sulphuric  acid  to 
75  c.c.  water,  and  put  in  it  some  of  your  starch.     Boil  gently 
for  twenty  minutes,  add  powdered  chalk  until  the  litmus  test 
indicates  no  acid,  and  boil  for  five  minutes  more.     Filter  and 
boil  in  the  evaporating  dish  to  a  thick  sirup.     Take  care  not 
to  burn  it.     Taste  some.    Conclusions  ?   Test  some  for  starch. 
What  has  happened?     Save  the  rest  for  (d). 

d.  Place  some  of  the  material  in  a  little  water,  and  warm  to 
dissolve  any  sugar  whfoh  may  be  present.     Add  a  drop  or  two 
of  sulphuric  acid  and  some  Fehling's  solution.     If,  upon  boil- 
ing, the  blue  color  changes  gradually  to  red,  grape  sugar  is 
present.     If  test  is  not  decisive,  add  more  Fehling's  solution 
and  continue  to  boil.     In  this  way  test  the  material  from  (c) 
and  also  the  materials  brought  from  home. 

e.  Cut  the  material  into  small  pieces,  and  pour  benzine  or 
ether  on  them.     After  a  few  minutes  filter,  and  let  the  solvent 


FOOD  ANALYSIS  267 

evaporate  in  a  clean  dish;   the  oil  which  remains  came  from 
the  material  tested.     In  this  way  test  other  substances. 

/.  Place  the  material  to  be  tested  in  a  test  tube,  and  pour 
over  it  concentrated  nitric  acid.  A  yellow  color  indicates  a 
proteid.  Wash  the  substance  and  add  a  little  ammonium 
hydrate.  A  dark  orange  is  a  sure  test  for  a  proteid.  Another 
test  is  to  burn  a  little  of  the  material.  The  odor  of  burning 
feathers  indicates  the  presence  of  a  proteid. 

Experiment  87.  —  Food  Preservatives  and  Colors. 

Apparatus :  Ring  stand,  burner,  asbestos  mat,  evaporating 
dish,  funnel,  pipette. 

Materials  :  Concentrated  sulphuric  acid,  ether,  gasoline, 
ferric  chloride  solution,  1  per  cent,  formaldehyde  test  solution 
(add  1  c.c.  of  10  per  cent  ferric  chloride  solution  to  1000  c.c. 
concentrated  hydrochloric  acid),  barium  chloride  solution, 
10  per  cent,  chloroform,  bromine  water,  filter  paper,  turmeric 
paper,  litmus  paper,  baking  soda,  concentrated  nitric  acid, 
concentrated  hydrochloric  acid,  ammonium  hydrate. 

a.  Test  for  copper:  Place  substance  in  evaporating  dish 
and  burn  it  with  strong  sulphuric  acid  and  heat.  Add  nitric 
acid,  a  little  at  a  time,  until  all  carbon  is  removed.  Add  a 
little  hydrochloric  acid  to  ash,  filter,  and  add  ammonium  hy- 
drate. A  blue  color  indicates  copper.  ' 

6.  Test  for  anatto:  Make  the  sample  of  milk  slightly  al- 
kaline with  baking  soda,  and  let  a  piece  of  filter  paper  remain 
in  it  for  a  day.  If  the  paper  is  stained  a  reddish  yellow,  there 
is  anatto  present.  Anatto  is  harmless,  but  it  is  put  into  milk 
with  intention  to  deceive. 

c.  Test  for  formaldehyde:  Add  formaldehyde  test  solution 
to  the  material,  and  warm  nearly  to  boiling.  A  violet  color 
indicates  formaldehyde. 


268         INTRODUCTION  TO  GENERAL  SCIENCE 

d.  Test  for  borates  or  boric  acid:  Treat  as  in  (a)  without 
the  addition  of  ammonium  hydrate.     If  turmeric  paper  is  wet 
with  mixture  and  turns  red  upon  drying,  there  is  boric  acid,  or 
some  borate,  present. 

e.  Test  for  sulphites  or  sulphurous  acid :  odor,  that  of  burn- 
ing matches.    Add  little  bromine  water,  and  warm.    Then  add 
barium  chloride  solution.     White  precipitate  indicates  that 
there  had  been  some  sulphite  present. 

/.  Test  for  benzoates  or  benzoic  acid :  Add  one  tenth  vol- 
ume of  chloroform  and  a  few  drops  of  sulphuric  acid.  Do 
not  shake.  When  chloroform  has  separated,  remove  it  with  a 
pipette  and  allow  it  to  evaporate.  Crystal  plates  are  formed, 
and  they  give  off  pungent  odor  when  heated. 

196.    WATER  ANALYSIS 

There  are  a  few  simple  tests  which  may  be  applied  to  water, 
and  thereby  prevent  sickness  from  the  use  of  impure  water. 
It  does  not  follow  that  clear  and  sparkling  water  is  pure,  nor 
that  muddy  water  is  bad.  Chemical  tests  are  the  only  ones 
upon  which  complete  dependence  may  be  placed.  Even  the 
sense  of  smell,  or  that  of  taste,  may  pronounce  the  water  bad 
when  the  very  material  which  causes  the  disagreeable  effect 
is  beneficial.  Naturally,  however,  pure  water  contains 
nothing  but  air,  and  our  senses  do  detect  some  kinds  of  foreign 
matter,  but  not  all  kinds.  Poison  from  bacterial  action  can- 
not be  detected,  but  if  the  organic  material  is  plentiful  in  the 
water,  bacterial  poisons  should  be  suspected. 

There  may  be  considerable  quantities  of  solid  material  dis- 
solved in  water  and  the  water  still  be  harmless.  Thus  no 
harmful  effect  has  been  noticed  where  hard  water  has  been 
used  for  drinking  purposes. 


WATER  ANALYSIS  269 

References :  — 

1.  1501:135-139.  Drinking  Water. 

2.  1503  :  325.  Impure  Water. 

3.  1702  :  59-61.  Impurities  in  Water. 

4.  1703  :  43-45.  Water  and  its  Impurities. 

5.  1710:64-78.  Tests  for  the  Impurities  in  Water. 

a.    1706:474-475.     Simple  Tests  for  Impurities  in  Water. 

Experiment  88. —  Water  Analysis. 

Apparatus:  Ring  stand,  burner,  asbestos  mat,  evaporating 
dish,  several  test  tubes. 

Materials:  Potassium  permanganate  solution,  10  per  cent, 
silver  nitrate  solution,  5  per  cent,  nitric  acid,  1-4,  concentrated 
sulphuric  acid,  alcoholic  solution  of  castile  soap,  common  salt, 
distilled  water. 

a.  Boil  to  dryness  the  evaporating  dish  full  of  water.  The 
residue  is  the  total  solid  matter  contained  in  the  water.  Heat 
strongly  the  dried  material.  If  it  chars,  there  is  organic 
matter  in  the  water.  Prove  it  by  (6). 

6.  Fill  one  test  tube  half  full  of  distilled  water  and  another 
test  tube  half  full  of  faucet  water.     To  the  latter  add  a  bit 
of  paper,  and  to  both  a  few  drops  of  concentrated  sulphuric 
acid.     Now  add  enough  potassium  permanganate  solution 
to  color  each  liquid  the  same  tint  of  light  purple.     Heat  the 
tube,  containing  the  paper,  just  to  the  boiling  point,  and  note 
the  change.     Then  heat  the  other  tube.     Is  there  any  change? 
To  test  a  sample  of  water  for  vegetable  material,  add  a  little 
potassium  permanganate  and  a  few  drops  of  concentrated 
sulphuric  acid,  and  heat  to  boiling.     Bring  a  sample  of  water 
from  home,  or  from  some  puddle,  and  test  it. 

c.  Add  a  little  salt  to  a  test  tube  half  full  of  water,  put  in  a 
few  drops  of  nitric  acid,  and  then  add  a  few  drops  of  silver 
nitrate.  The  result  is  silver  chloride.  Describe  it.  This 


270         INTRODUCTION  TO  GENERAL  SCIENCE 

is  the  test  for  chloride,  and  water  which  gives  this  result  with 
nitric  acid  and  silver  nitrate  may  contain  animal  matter. 
Bring  a  sample  of  water  and  test  it.  Always  add  the  nitric 
acid  first. 

d.  Hardness  can  be  indicated  by  seeing  how  much  soap 
is  necessary  to  produce  a  strong  lather.  To  half  a  test  tube 
of  distilled  water,  add  a  very  little  soap  solution,  cover  the 
open  end  with  the  thumb,  and  shake.  See  if  the  lather  will 
last  three  minutes.  If  not,  add  a  little  more  soap  solution. 
Now  test  a  sample  of  water  and  see  how  much  more  soap  is 
needed  to  produce  the  same  result.  Why  is  hard  water  said 
to  be  expensive  to  use? 

197.    FOOD  —  PRESERVATION  OF  FOOD 

Bacteria  and  molds,  as  well  as  other  microorganisms,  live 
upon  the  same  food  as  do  man  and  the  other  animals.  For 
that  reason  we  must  prevent  these  undesirable  organisms 
from  entering  our  food.  This  can  be  accomplished  by  heat- 
ing, drying,  salting,  and  smoking  the  material  to  be  preserved; 
and,  in  some  cases,  a  large  proportion  of  sugar  will  prevent 
the  unfavorable  growths.  It  may  be  necessary  to  inclose  the 
food  in  a  bacteria-  and  mold-proof  container. 

Coolness  and  cleanliness  will  prevent  the  unnecessary 
introduction  and  rapid  growth  of  bacteria.  Eggs  may  be 
preserved  by  immersing  them  in  a  10  per  cent  solution  of 
water  glass. 

References :  — 

1.  1710 :  297-307.  Preservation  of  Food. 

2.  1901 : 139-156.  Preservation  of  Food. 

3.  1901 :  157-168.  Use  of  Preservatives. 

4.  1901 : 169-181.  Preservation  by  Canning. 


THE  MIND  271 

5.  Farmers'  Bulletin  No.   122:29-31.     Preparation  of  Unfer- 

mented  Grape  Juice. 

6.  Farmers'  Bulletin  No.  175.     Home  Manufacture  and  Use  of 

Unfermented  Grape  Juice. 

7.  Farmers'  Bulletin  No.  203.     Canned  Fruits,  Preserves,  and 

Jellies. 

8.  Farmers'    Bulletin   No.    359.     Canning   Vegetables    in   the 

Home. 

9.  Farmers'  Bulletin  No.  375.     Care  of  Food  in  the  Home. 

10.    Farmers'  Bulletin  No.  413.     The  Care  of  Milk  and  its  Use 

in  the  Home. 

a.    1506 :  46-53.         Microbes  and  Molds. 
6.    1902  :  236-250.     Preservation  of  Food. 

c.  1903  :  42-43.         Salts  and  Sugar  as  Preserving  Agents. 

d.  1904 : 153.  The  Care  of  Foods. 

198.    THE  MIND 

The  distinguishing  feature  which  differentiates  man  from 
other  animals  is  his  mind.  The  more  he  uses  his  mind,  along 
the  right  direction,  the  less  an  animal  he  becomes.  Never- 
theless, since  the  brain  is  the  organ  of  the  mind,  and  since  the 
brain  is  a  physical  organ,  the  mind  is  necessarily  affected  by 
changes  in  the  body. 

If  the  organs  of  digestion  are  not  performing  their  work 
properly,  the  brain  is  temporarily  affected  and  the  person 
becomes  irritable.  It  is  quite  a  question  as  to  the  true  re- 
sponsibility for  his  ill-nature,  under  these  conditions.  The 
old  saying  that  "  the  way  to  reach  a  man's  heart  is  through 
his  stomach,"  contains  as  much  physiological  truth  as  it  does 
common  sense.  Unless  the  body  is  normal,  the  mind  cannot 
act  as  it  would  under  more  favorable  circumstances. 

It  must  be  remembered,  however,  that  the  mind  can  exert 
an  influence  over  the  body,  controlling  it  and  refining  it, 
through  education,  to  the  highest  ideals  of  mankind. 


272         INTRODUCTION  TO  GENERAL  SCIENCE 

References :  — 

1.  1501 :  305-320.          Influences  which  Affect  the  Mind. 

2.  1503  :  400-418.  The  Nervous  System. 

a.  1505  :  117-141.     The  Nervous  System. 

b.  1506 :  215-244.     The  Nervous  System  and  the  Senses. 

c.  1507 : 321-327.     Care  of  the  Brain ;    Disease  of  Nervous 

System. 

d.  1507 : 328-339.     A  Clear  Mind  the  Need  of  the  Day. 

e.  1509 :  241-245.     Use  and  Care  of  the  Nervous  System. 
/.    1511:252-253.     The  Mind. 


199.    THE  SENSES  — SIGHT 

Most  animals  have  five  senses:  sight,  hearing,  smell, 
taste,  and  feeling.  These  senses  are  all  for  use;  if  they  are 
not  used,  they  become  weakened,  and  certain  senses  may  be 
lost  entirely.  Thus  fish  in  underground  waters,  not  needing 
to  see,  have  no  eyes.  The  ability  to  see  and  to  hear  enables 
animals  to  guard  against  the  approach  of  enemies,  as  well  as 
to  help  them  secure  their  own  food.  With  the  lower  animals 
the  sense  of  smell  aids  in  a  similar  way. 

With  man,  in  the  civilized  state,  the  use  of  the  senses,  es- 
pecially those  of  smell  and  hearing,  is  not  so  apparent.  All  our 
senses  are  to  protect  us,  or  help  us,  and  we  should  not  neglect 
their  warnings.  Pain  signifies  that  there  is  some  local  trouble. 
We  should  try  to  correct  the  trouble,  and  the  pain  will  pass 
away,  since  there  is  no  longer  any  need  of  a  warning.  To 
stop  the  pain  by  paralyzing  the  nerves,  without  curing  the 
ailment,  is  to  take  away  from  the  body  its  protection.  A  bad 
odor  or  a  bad  taste  signifies  that  there  are  decay,  bacteria, 
and  possibly  disease  in  the  material  producing  the  odor  or 
taste.  The  warnings  of  the  senses  must  be  heeded. 

The  sense  of  sight  is  the  one  which,  without  doubt,  gives  us 


SIGHT  273 

the  most  pleasure  and  the  greatest  feeling  of  security.     The 
eye  is  by  far  the  most  sensitive  sense  organ. 

References :  — 

1.  1501 :  323-325.  Taste  and  Smell. 

2.  1501 :  333-344.  The  Eye. 

3.  1503  :  419-427.  The  Senses. 

4.  1803:435-437.  The  Eye  —  Vision. 
a.    1505:142-157.  The  Senses. 

6.  1506 :  237-242.  The  Sense  Organs. 

c.  1506:246-249.  The  Eye. 

d.  1507 :  340-361.  The  Eye  and  Light. 

e.  1509  :  246-275.  The  Special  Senses. 

/.    1510 :  114-116.     The  Value  of  the  Nerves.  —  Sense  Organs. 

g.    1511 :  314-366.     The  Special  Senses. 

h.    1806  :  152-154.     The  Eye.     Color  Sensation. 

Experiment  89.  —  Persistence  of  Vision.  —  Fatigue. 

Apparatus:    Piece  of  cardboard  2"  X  2",  string,  colored 
cards  —  red,  bluish  green,  yellow,  blue,  purple. 

a.  Punch  a  hole  in  each  of  two  opposite  ends  of  the  card- 
board, and  in  each  tie  a  string  in  a  loop  about  eight  inches 
long.  Draw  the  head  of  a  man  on  one  side  and  some  parallel 
lines  (to  represent  prison  bars)  on  the  other  side.  To  "  put 
the  man  in  prison  "  cause  the  piece  of  cardboard  to  revolve 
rapidly  by  putting  the  loops  over  your  two  thumbs  and  turn- 
ing the  cardboard  until  it  winds  up  the  string  in  spirals,  then 
gently  pull  the  hands  apart.  The  impression  which  the  eye 
receives  from  one  side  of  the  cardboard  lasts  until  the  other 
side  is  seen.  Therefore  both  seem  to  be  seen  simultaneously. 
This  will  explain  the  moving  pictures  wherein  a  series  of  pic- 
tures are  thrown  on  a  screen  with  less  than  a  tenth  of  a  second 
between  successive  ones.  The  impression  from  one  lasts 
until  another  is  seen. 
T 


274         INTRODUCTION  TO  GENERAL  SCIENCE 

b.  Look  steadily  for  one  minute  at  the  red  card,  and  then 
immediately  look  at  a  white  paper  or  wall.  What  color  do 
you  see?  You  will  remember  that  white  is  composed  of  all 
the  other  colors.  Now  the  eye  is  tired  from  seeing  one  color, 
and  responds  to  the  other  colors  contained  in  the  white.  The 
blending  of  these  other  colors  is  what  produces  the  apparent 
color.  Repeat  with  the  other  cards,  and  tabulate  your  results. 
The  color  which  appears  to  be  present  on  the  white  is  called 
the  complementary  color  of  the  original  color. 

200.    SOUND  AND  HEARING 

Sound  is  caused  by  some  material  body  moving  to  and  fro, 
that  is,  vibrating  at  least  sixteen  times  a  second.  Impulses 
are  sent  out  which  are  conveyed  by  the  air.  There  must  be 
some  material  medium,  or  sound  will  not  be  carried  from  its 
source.  Liquids  carry  sound  better  than  gases,  and  solids 
better  than  liquids.  In  each  case,  usually,  the  sound  must 
originate  in  the  medium  which  is  to  convey  it.  We  receive 
the  sensation,  which  we  call  sound,  due  to  the  beating  of  the 
vibrations  of  the  air  upon  the  eardrums,  which,  in  turn,  con- 
vey the  vibrations  within,  to  the  nerves.  Vibrations  coming 
at  regular  intervals  are  musical  sounds;  other  vibrations 
cause  merely  noise. 

As  we  understand  it,  sound  is  the  sensation,  and,  while  the 
vibrations  would  exist  even  if  there  were  no  ears  to  hear,  yet 
sound  does  not  exist  outside  of  the  nervous  system.  In  this 
respect,  sound  and  light  are  similar,  —  both  are  sensations. 

References :  — 

1.  1501 :  325-330.  The  Ear  and  Hearing. 

2.  1501:349-353.  The  Voice.      . 

3.  1503:421-422.  The  Organ  of  Hearing. 


SOUND   AND   HEARING  275 

4.  1803  :  343-344.  Sources  of  Sound. 

5.  1803  :  351-352.  Musical  Sounds  and  Noises. 

a.  1506 :  241-244.  The  Sense  of  Hearing  —  the  Ear. 

6.  1507  :  362-373.  The  Ear  and  Sound. 

c.  1509  :  252-256.  Hearing  and  Sound. 

d.  1801 :  140-152.  Sound  ;  its  Transmission  and  Velocity. 

e.  1804 :  186-197.  Origin  of  Sound  and  its  Transmission. 
/.  1805  :  169-180.  Waves  —  Sounds  ;  its  Transmission. 
g.  1805  :  192-195.  Characteristics  of  Sound. 

h.    1806 :  441-444.     Sound  ;  its  Sources  and  Transmission. 

i.    1808 :  163-165.     The  Nature  of  Sound. 

j.    1808  :  180.  Properties  of  Musical  Tones. 

Experiment  90.  —  The  Origin  of  Sound.  —  Music. 

Apparatus:  A  vise  or  clamp,  piece  of  clock  spring,  pins, 
hammer,  piece  of  wood. 

a.  Fasten  the  piece  of  clock  spring  in  the  vise  so  that  a  six- 
inch  section  of  it  is  free  to  move.  Cause  it  to  vibrate.  Does 
it  produce  a  musical  tone?  Shorten  the  free  end  of  the  spring, 
and  vibrate  again.  What  is  the  result?  Continue  to  shorten 
the  spring.  What  happens,  and  what  is  the  final  result? 
What  is  the  origin  of  sound? 

6.  Drive  a  pin  into  a  piece  of  wood,  and  make  it  vibrate. 
Note  the  tone.     Now  drive  another  pin  a  little  deeper  into 
the  wood,  trying  to  cause  the  pin  to  give  forth  the .  next 
higher  note  in  the  ordinary  musical  scale.     In  this  manner 
drive  six  more  pins,  completing  the  scale. 

c.  After  the  practice  in  (6)  try  driving  in  a  row  of  pins 
which  will  play  some  simple  air  when  they  are  caused  to 
vibrate  in  succession. 

Experiment  91. — The  Megaphone  and  Mechanical  Tele- 
phone. 

Apparatus:  Two  tin  vegetable  cans,  or  baking  powder  tins, 
string,  brass  rivets  for  paper,  scissors. 


276          INTRODUCTION  TO  GENERAL  SCIENCE 

Materials:  Sheet  of  bristol  board,  22"  X  28". 

a.  To  make  a  megaphone:  Tie  a  string  two  feet  long  to  a 
pencil,  and  with  a  radius  of  twenty-two  inches,  using  one 
corner  of  the  bristol  board  as  a  center,  draw  as  long  an  arc  as 
possible  on  the  paper.  With  the  same  point  as  a  center,  and 
with  a  radius  of  four  inches,  describe  another  arc.  Cut  the 
bristol  board  along  the  lines.  Now  roll  up  the  bristol  board 
to  form  a  funnel,  and  fasten  every  five  or  six  inches,  along 
the  edge,  with  the  paper  rivets. 

6.  Send  your  partner  a  hundred  feet  away,  and  speak  to  him 
in  an  ordinary  tone  of  voice.  He  will  probably  not  hear  you. 
Now  place  the  small  end  of  your  megaphone  to  your  lips, 
direct  the  large  end  toward  your  partner,  and  speak  to  him 
in  the  same  tone  of  voice.  Does  he  hear  you?  Have  your 
partner  speak  to  you  in  the  same  manner.  Go  so  far  away 
from  your  partner  that  you  can  just  carry  on  a  conversation 
by  means  of  the  megaphone.  Does  the  megaphone  help? 
The  megaphone  prevents  the  vibrations  of  the  voice  from 
spreading,  and  guides  them  in  the  desired  direction. 

c.  Punch  a  hole  in  the  center  of  the  bottom  of  the  cans, 
with  a  nail.  Push  a  string  through  the  hole  in  each,  and  tie 
a  knot  in  it  to  keep  it  from  slipping  through  again.  The 
cans  should  be  separated  by  a  string  at  least  one  hundred 
feet  long.  Hold  the  can  to  your  mouth  and  have  your  partner 
hold  his  can  to  his  ear.  Try  whispering  to  him.  Have  him 
repeat  your  actions.  The  string  must  be  held  taut,  for  it 
carries  the  vibrations,  and  the  more  characteristics  of  a  solid 
which  it  has,  the  better  will  the  vibrations  be  carried. 

A  telephone  like  this  may  be  used  for  a  distance  of  one 
mile.  Very  satisfactory  results  may  be  obtained  by  the  fol- 
lowing method:  At  each  end  of  the  line  a  board,  one  foot 
wide,  should  be  fitted  in  a  window.  In  the  board  should  be 


MAN'S  PLACE  IN  NATURE  277 

cut  a  hole  so  that  a  large-sized  lard  pail  will  just  fit  it.  Fasten 
the  pail  so  that  it  will  project  outside,  with  its  open  end 
inside.  To  do  this,  drive  several  nails  radically  from  the 
inside  edge  of  the  pail,  through  it  into  the  board.  A  small 
hole  should  be  punched  in  the  exact  center  of  the  bottom  of 
the  pail,  to  receive  a  wire,  No.  20,  galvanized  iron.  The 
end  of  the  wire  should  be  passed  through  a  washer  and 
fastened.  The  wire  must  be  supported,  if  it  is  longer  than 
two  hundred  feet,  by  loops  of  tarred  cord,  at  least  six  inches 
long.  This  allows  free  movement  of  the  wire.  For  this  rea- 
son the  wire  should  not  touch  anything  except  the  tarred 
cord.  To  call  your  party,  knock  on  the  bottom  of  the  pail. 
The  noise  will  be  about  equal  at  both  ends  of  the  line. 


201.    MAN'S  PLACE  IN  NATURE 

Information  concerning  man  may  be  obtained  from  geology, 
biology,  and  history.  The  last-named,  so  far  as  the  records 
show,  tells  us  only  of  the  last  few  thousands  of  years.  Geo- 
logical records,  left  in  the  enduring  rock,  as  it  is  sometimes 
called,  indicate  that  man  lived  almost  countless  thousands  of 
years  before  any  other  records  were  made.  In  addition,  it 
must  be  remembered  that  rock  itself  disintegrates  and  may 
be  changed  into  other  kinds  of  rocks*.  Therefore,  it  is  very 
probable  that  man  existed  long  before  the  time  which  is  indi- 
cated by  any  of  the  geological  records. 

Biology,  in  its  study  of  life  from  the  single-celled  amoeba 
up  through  all  forms  and  aggregations  of  cells;  in  its  classi- 
fications of  all  animal  life  by  structure  and  by  habits,  has 
placed  man  far  above  all  other  animals  among  the  vertebrate 
mammals  called  the  primates.  See  Section  183,  Animal 
Life  —  Man. 


278  INTRODUCTION   TO  GENERAL  SCIENCE 

While  man,  due  to  his  intelligence,  may  rise  superior  to 
circumstances  and  environment,  yet  he  is  entirely  dependent 
upon  nature.  All  possible  mental  attainments  cannot  free 
man  from  the  necessity  of  supplying  his  animal  needs.  He 
requires  air  to  breathe,  water  to  drink,  and  food  to  eat.  He 
suffers  pain  and  discomfort  as  does  any  other  animal,  and  must 
pay  the  penalty  of  wrong  living  as  any  animal  must.  Never- 
theless, above  and  beyond  all  this,  man's  mind,  through  edu- 
cation of  mind  and  body,  may  rise  superior  and  cause  him 
to  merit  truly  the  title  of  "  Lord  of  Creation." 

References :  — 

1.  1205 :  414.  Man  a  Primate. 

2.  1304  : 369-375.  Man  and  Nature. 

3.  1503  :  316.  Man's  Place  in  Nature, 
a.    1302  :  383-384.  The  Ascent  of  Man. 

6.    1303:345-346.     Races  of  Mankind. 

c.  1305:350-358.     Man. 

d.  1307:334-335.     Man. 


202.    NATURE  AND  BUSINESS 

* 

The  natural  conditions  in  which  man  finds  himself  have  a 
great  effect  upon  the  kind  of  business  which  he  will  pursue, 
and  his  character  in  some  special  direction.  This  is  especially 
true  of  uncivilized  man,  for  nature  is  his  master.  As  knowl- 
edge and  inventiveness  increase,  man  gains  a  mastery  over 
nature  and  alters  many  of  those  conditions  which  are  unsatis- 
factory to  him. 

The  business  of  a  nation  is  affected  similarly  to  the  life  of 
the  individual.  Mountains  and  plains,  bays  and  harbors, 
all  influence  business,  which  follows  the  paths  of  least  resist- 
ance unless  great  gain  is  expected.  Any  desirable  feature 


APPLICATION  OF   NATURE'S  PRINCIPLES       279 

which  is  lacking  must  be  supplied,  and  so  we  find  nations 
bridging  chasms,  burrowing  through  mountains,  building 
harbors  and  breakwaters,  and  joining  oceans  by  canals. 
Knowledge  always  rises  superior  to  environment  and  makes 
its  own  conditions. 

References :  — 

1.  1304 :  377-379.          Development  of  Commerce. 

2.  1304  :  379-380.  Influence  of  Man  on  Nature. 

a.  1302  :  391-392.     The  Development  of  Natural  Resources. 

b.  1303  :  364-367.     Geographical  Factors  in  the  Life  of  Civil- 

ized Peoples. 

c.  1305  :  365.  Causes  of  Civilization. 

d.  1307  :  349-351.     Man's  Relation  to  Physiography. 

e.  1308 :  125-142.     Man's  Relation  to  Natural  Conditions. 
/.    1308  :  192-211.     Nature  of  Trade  Routes  and  Stations. 
g.    1311 :  369-370.     Man's  Influence  on  Nature. 


203.    MAN'S  APPLICATIONS  OF  NATURE'S  PRINCIPLES 

The  great  inventions  and  the  wonderful  machines  which 
man  has  made  are  but  the  application  of  natural  law.  Man 
cannot  change  the  laws  of  nature,  but  he  can  produce  condi- 
tions which  are  favorable  for  the  action  of  those  laws,  direct- 
ing and  controlling  them  so  that  they  may  accomplish  what 
he  desires.  Man  discovers,  and  applies  the  knowledge  of  his 
discoveries;  he  cannot,  in  the  true  sense,  produce  or  create. 
Nature  is  the  great  prime  mover. 

A  few  of  the  direct  applications  of  natural  law  are :  heating 
by  condensation,  cooling  by  evaporation  and  expansion,  clean- 
ing by  partial  vacuum,  power  from  explosions  and  expansion, 
transmission  of  power  by  water,  compressed  air,  and  elec- 
tricity, the  production  of  electricity  and  all  of  its  uses.  On  the 


280  INTRODUCTION  TO  GENERAL  SCIENCE 

biological  side  there  are  the  production  of  new  plants  by  direct- 
ing their  propagation,  the  control  of  bacteria,  and  many  medi- 
cal discoveries. 

References :  — 

a.  1305 :  372.  Man's  Control  over  Nature. 

b.  1308:126-130.     Human    Adaptation. —  ''Conquest    of    Na- 

ture." 

c.  1309 :  319-321.     Man's  Influence  upon  Physical  Geography. 

d.  1311:353-354.     Fuel  and  Light. 


204.    How  TO  PLAN  A  HOUSE  AND  BARN 

The  heart  of  a  house  is  its  kitchen.  This  is  the  room  in 
which  the  housewife  spends  more  than  half  of  her  time,  and  it 
should  have  more  thought  given  to  it  than  to  any  other  part 
of  the  house.  The  beautiful  and  the  artistic  should  not  be 
neglected,  but,  if  the  beautiful  objects  require  extra  work,  or 
cause  inconvenience,  they  should  be  removed  or  altered. 
On  the  other  hand,  conveniences  need  not  be  ugly,  and  may 
be  beautiful. 

The  kitchen  should  be  planned  first  and  the  rest  of  the 
house  adapted  to  the  plan  of  the  kitchen.  The  coldest  part 
of  the  house,  that  is,  the  northern  side,  or  corner,  should  be 
reserved  for  the  kitchen.  Where  possible,  the  corners  of  the 
house  should  point  to  the  four  points  of  the  compass.  This 
will  give  sunlight  in  every  room,  part  of  each  day.  In  a  two- 
story  house,  the  dining  room  should  be  on  the  eastern  corner. 
Unless  a  library  is  desired,  the  rest  of  the  lower  story  should  be 
given  to  one  large  room.  In  this  case,  the  bathroom  should 
be  as  nearly  over  the  kitchen  as  possible,  to  save  in  plumbing. 
At  the  same  time,  it  should  be  between  two  of  the  bedrooms, 


HOW   TO  PLAN  A   HOUSE  281 

with  doorways  from  each  opening  into  it,  as  well  as  a  third 
doorway  opening  into  the  upper  hall.  * 

In  a  one-story  building,  the  kitchen  should  be  on  the 
eastern  corner,  the  living  room  on  the  southern  corner,  and 
the  dining  room  between.  The  other  side  of  the  house  should 
contain  the  bedrooms  and  the  bathroom.  Each  bedroom 
should  have  a  large  closet  with  a  window  in  it.  Closets  should 
not  be  crowded  in,  here  and  there,  but  the  house  should  be 
made  large  enough  to  contain  the  space  necessary  for  proper 
closets. 

Instead  of  having  the  toilet  in  the  bathroom,  it  is  an  excel- 
lent plan  to  have  separate  rooms  with  toilet  in  one  of  them, 
and  the  bathtub  and  lavatory  in  the  other.  The  low  tank 
toilet  is  the  best  pattern. 

Returning  now  to  the  kitchen :  The  sink  should  be  against 
an  inside  wall  with  a  window  at  the  left.  The  ^bottom  of 
the  sink  should  be  at  such  a  height  that  it  can  be  reached 
with  the  extended  fingers  when  its  user  stands  erect.  This 
brings  the  sink  higher  than  is  usual,  but  is  the  proper  height 
to  prevent  an  aching  back  and  rounded  shoulders.  Under- 
neath the  sink  there  may  be  a  shelf,  but  the  space  should  not 
be  inclosed,  as  such  a  closet  is  liable  to  be  unsanitary. 

The  stove  should  be  placed  as  far  from  the  sink  as  possible, 
so  that  a  person  can  wash  the  dishes  without  suffering  unnec- 
essarily from  the  heat.  This  will  bring  the  stove  into  the 
diagonally  opposite  corner,  with  a  window  at  its  right.  Cook- 
ing utensils  should  be  hung  near  the  stove. 

The  other  inside  wall  should  have  cupboards  for  dishes  and 
the  storage  of  food.  In  the  outside  wall,  next  to  a  screened 
porch,  if  possible,  there  should  be  a  cold  closet  and  an  ice 
chest,  the  latter  arranged  to  receive  ice  from  outside.  The 
cold  closet  should  have  a  bottom  air  inlet,  running  from  out- 


282         INTRODUCTION  TO  GENERAL  SCIENCE 

doors  and  not  from  under  the  house,  and  a  top  air  outlet 
running  up  the  outside  of  the  house  and  painted  black.  This 
outlet  pipe  becomes  heated  and  produces  a.  current  of  cool  air 
through  the  cold  closet.  See  Section  205,  Conveniences  for 
the  Home.  See  references  for  plans  of  barns. 
References :  — 

1.  1501:253.     Choice  of  a  House. 

2.  Farmers'  Bulletin  No.  126.     Practical  Suggestions  for  Farm 

Buildings. 

3.  Farmers'   Bulletin  No.  342:30-32.     A  Model  Kitchen. 

4.  Bureau  of  Animal  Industry,  Circular  131.     Designs  for  Dairy 

Buildings. 
a.   1507:386-389.     The  Home. 

205.    CONVENIENCES  FOR  THE  HOME 

There  is  perhaps  no  better  example  of  custom  being  handed 
on  from  generation  to  generation  than  is  shown  in  the  home. 
Women  are  expected  to  use  the  same  kind  of  utensils  and  appli- 
ances, as  well  as  to  endure  the  same  inconveniences,  as  their 
mothers  did.  Man  has  improved  his  workshops  and  factories, 
but  the  business  of  the  house  has  been  neglected  until  recently. 
Now  there  are  many  conveniences,  some  of  whicn  are  inex- 
pensive, while  others  are  quite  costly.  The  expensive  ones, 
however,  are  long-lived  and  are  cheap  in  the  end,  when  the 
great  saving  of  energy  and  time  on  the  part  of  the  housewife 
is  taken  into  consideration.  Housework  is  a  necessity,  but 
there  is  no  reason  why  it  should  approach  slavery. 

The  workshop  of  the  house  is  the  kitchen.  This  should  be 
made  moderately  small  and  have  everything  convenient  in 
order  to  save  miles  of  walking.  Many  things  may  be  done 
while  sitting,  and  an  office  stool  should  be  in  every  kitchen. 
This  may  be  slid  under  a  shelf  when  not  in  use. 


CONVENIENCES  FOR   THE  HOME  283 

Just  as  a  good  workman  may  get  along  with  poor  tools,  yet 
cannot  work  to  the  best  of  his  ability  without  good  ones,  so 
a  housekeeper  needs  the  best  that  can  be  obtained  in  the  way 
of  labor-saving  appliances  and  utensils.  A  few  of  the  con- 
veniences and  some  of  the  necessities  which  may  be  mentioned 
are  as  follows :  — 

Enamel  sink  and  wooden  drying  boards  on  each  side;  hot 
and  cold  water  at  sink,  and  cold  water  faucet  made  to  swing 
over  the  stove;  faucet  attachment  to  prevent  spattering  of 
water;  scraper,  made  of  rings,  for  removing  burned  material 
from  pots;  scraper,  made  with  flat  rubber  edge,  for  removing 
grease  from  table  dishes;  strainer  at  sink,  to  prevent  matter 
going  down  the  drainpipe;  bottle  washer  which  can  be  used 
for  glass  chimneys;  polishing  cloth  for  .silver;  kitchen  cook- 
ing cabinet,  portable  or  built-in;  kitchen  table,  with  bins  and 
drawers,  as  second  choice  for  kitchen  cabinet;  billhook  for 
keeping  store  slips  in  the  order  in  which  they  come;  card 
index,  made  of  heavy  envelopes,  for  saving  recipes;  standard 
measuring  spoons ;  glass  measuring  cup ;  scales;  meat  grinder; 
vegetable  slicer;  potato  ricer,  for  making  mashed  potatoes  or 
aiding  in  the  reduction  of  any  vegetable  to  a  paste;  electric, 
water-power,  or  even  hand-power,  washing  machine,  where 
the  laundry  work  is  performed  at  home;  electric  or  alcohol 
iron;  chemical  dust  rag  which  picks  up  the  dust;  a  yacht 
mop  for  dusting  hardwood  floors.  Besides  these,  the  house- 
keeper should  have  anything  else  which  will  make  the  work 
easier  and  save  time. 

The  walls  of  the  kitchen  and  the  bathroom  should  be 
covered  with  hard  paint,  or  washable  wall  paper,  of  a  light 
tint.  The  floors  of  both  rooms  should  be  covered  with 
linoleum. 


284         INTRODUCTION  TO  GENERAL  SCIENCE 

References :  — 

1.  Farmers'  Bulletin  No.  270.     Modern  Conveniences  for  the 

Farm  Home. 

2.  Farmers'  Bulletin  No.  317 :  5-9.     The  Farm  Home. 

3.  Reprint  from  Yearbook  Department  of  Agriculture  for  1909  : 

Comforts  and  Conveniences  in  Farmers'  Homes. 


206.    SANITATION 

"  Sanitation  "  comes  from  the  same  source  as  the  word 
sanity,  and  the  two  should  go  hand  in  hand.  Conditions 
are  now  no  worse  than  they  were  hundreds  of  years  ago,  when 
little  was  known  and  less  was  thought  on  the  subject  of  sani- 
tation. Now  we  know  the  causes  of  many  diseases,  and  that 
they  owe  their  origin  to  unsanitary  conditions.  For  that 
reason  there  are  some  persons  who  seem  to  think  that  the 
fault  lies  in  knowing  too  much,  and  that  if  we  did  not  recog- 
nize the  presence  of  bacteria,  they  would  do  no  harm.  We 
cannot  afford  to  fail  to  recognize  the  true  conditions,  and  we 
should  take  steps  to  remedy  the  conditions  according  to  our 
knowledge  of  sanitation  and  sanitary  measures. 

There  are  bacteria  everywhere,  in  everything.  Many  are 
necessary,  and  even  the  bacteria  of  decay,  which  trouble  the 
housewife,  are  of  great  value  in  the  production  of  soil  and  the 
removal  of  plant  and  animal  waste.  On  the  other  hand, 
disease  bacteria  are  very  liable  to  be  present  in  putrefaction, 
and  we  must  guard  ourselves  against  their  attacks. 

Cleanliness  and  neatness  are  sanitary  measures.  In  fact, 
if  there  were  no  contamination  from  the  outside,  cleanliness 
would  be  a  sufficient  guard  against  disease.  We  should  not 
allow  the  refuse  from  the  kitchen  to  accumulate  even  for  a 
few  days.  The  decaying  material  serves  as  a  place  where 


SANITARY  PLUMBING  285 

flies  lay  their  eggs.  The  flies  carry  disease  germs  into  the 
house  and  contaminate  food.  If  a  neighborhood  did  not 
feed  the  flies,  there  would  be  no  flies. 

The  drainage  from  the  toilets,  and  even  from  the  kitchen 
sink,  should  be  taken  care  of  in  the  best  possible  way.  Cess- 
pools are  not  very  satisfactory  under  the  best  conditions,  as 
the  seepage  may  go  where  it  will  do  harm.  The  septic  tank 
system,  wherein  bacteria  change  the  material  into  substances 
which  are  harmless,  is  the  best,  where  there  is  no  regular 
system  of  drainage.  See  next  section. 

Personal  cleanliness  is  a  part  of  sanitary  living.     Bedrooms 
should  be  well  ventilated  and  closets  for  clothes  should  have 
windows  in  them.    Sunshine  is  the  greatest  germ  killer  known, 
and  every  room  should  have  as  much  sunshine  as  possible. 
References :  — 

1.  1702:361-362.  Sanitary  Conditions. 

2.  1710 :  74-78.  Drinking  Water  and  Disease. 

3.  1901 :  151-154.          A  Sanitary  Ice  Chest. 

4.  1901 :  253-254.  General  Rules  of  Sanitation. 

5.  Bureau   of  Animal   Industry,  Circular    158.     Production  of 

Market  Milk. 

a.  1502 :  473-475.  Sanitation  in  School. 

6.  1505  :  23-26.  Bathing  and  Clothing. 

c.  1505: 162-164.  Protection  against  Disease. 

d.  1506 : 187-189.  The  Bath.  —  Clothing  and  Health. 

e.  1507  :  244-248.  Care  of  the  Skin  and  Clothing. 
/.  1509  :  207-208.  Necessity  for  Cleanliness. 

g.    1511 :  288-297.     Care  of  the  Skin.  —  Bathing. 

h.    1904  :  187-192.     Practical  Sanitation. 

i.    1905 :  64-72.        The  Care  of  the  School  Building. 

207.    SANITARY  PLUMBING 

In  the  olden  times,  when  people  first  used  pipes  to  conduct 
waste  water  from  their  houses,  they  employed  straight  pipes; 


286         INTRODUCTION  TO  GENERAL  SCIENCE 

that  is,  pipes  without  certain  bends,  or  cavities,  which  are 
called  traps.  Under  those  conditions  the  gases  from  the 
decomposing  material  rose  in  the  pipes  and  entered  the  build- 
ings, carrying  bacteria.  The  common  name  for  this  gas 
is  sewer  gas,  and  it  should  not  be  allowed  to  enter  a  building 
under  any  circumstances. 

The  first  improvement  was  to  bend  the  pipe  into  an  S-shape, 
which,  turned  on  its  side,  produced  a  U  in  the  pipe.  In  this 
bend  water  was  expected  to  remain,  and  thus  prevent  the 
entrance  of  the  sewer  gas.  Under  favorable  conditions,  this 
form  of  trap  operated  successfully,  but  often  the  sewer  gas 
came  up  the  drainpipe,  notwithstanding  its  shape.  It  was 
then  discovered  that  the  traps  acted  as  siphons  and  were 
entirely  emptied  by  the  outgoing  stream.  To  prevent  the 
siphon  effect,  a  vent  pipe  was  connected  to  the  top  of  the  bend, 
and  this  pipe  was  run  up  through  the  roof  of  the  building. 
Not  only  is  the  trap  thus  prevented  from  emptying,  but  any 
accumulation  of  sewer  gas  is  led  off  from  the  pipes  without 
harm  to  the  dwellers  in  the  building. 

Every  drain  should  have  a  trap,  and  every  trap  should  have 
a  vent  pipe,  running  up  through  the  roof.  The^re  is  a  dan- 
gerous habit  of  using  one  trap  for  two  or  more  near-by  drains, 
and  it  should  be  discouraged.  On  the  other  hand,  one  vent 
pipe  can  be  safely  used  for  many  traps. 

There  should  be  a  large  trap  in  the  main  drain  where  it 
leaves  the  building.  This  trap  may  be  what  is  called  drum 
trap,  and  need  not  be  ventilated.  All  traps  should  have  a 
tightly  fitting  cover,  which  can  be  removed  for  purposes  of 
cleaning  out  any  solid  material  which  has  accumulated. 

Cesspools  should  be  vented,  and  the  vent  pipe  should  run 
up  high  enough  to  prevent  any  annoyance  from  the  gases. 

It  must  be  remembered,  however,  that  even  sanitary  plumb- 


SIMPLE  HOUSEHOLD  REMEDIES  287 

ing  may  become  unsanitary  through  carelessness.  Grease 
will  gradually  stop  up  the  sink  drain  if  hot  water  is  not  poured 
down  it  occasionally,  while  the  toilet  drain  may  be  blocked  by 
paper  or  rubbish.  It  is  a  good  plan  not  to  throw  anything 
into  the  toilet.  If  the  drains  do  become  stopped,  the  traps 
should  be  opened  and  cleaned  out.  Wire  No.  10  may  then 
be  used  to  force  or  pull  out  most  of  the  accumulated  material, 
and  a  saturated  solution  of  caustic  potash  can  be  poured 
into  the  pipes  to  remove  the  remaining  part. 
References :  — 

1.  1501 :  252-253.  Dangers  from  Sewage.  —  Plumbing. 

2.  1605  :  392-395.  The  Septic  Tank. 

3.  1901 :  246-248.  Sewage  and  Plumbing. 
a.    1507:394-395.     Sewage. 

6.  1511 :  137-139.  Cesspools  ;  Sewers  and  Plumbing. 

c.  1902  :  83-84.  The  Septic  Tank. 

d.  1903  : 112-114.  Bacterial  Purification  of  Sewage. 

e.  1904 :  193-194.  Building  a  Dry  Closet. 

/.    1905:60-64.         Sewage  Disposal  in  Schools. 

208.    SIMPLE  HOUSEHOLD  REMEDIES 

The  kitchen  closet  usually  contains,  for  domestic  purposes, 
enough  remedies  to  cure  ordinary  ailments.  A  person  should 
resort  to  the  use  of  medicines  as  little  as  possible,  but  it  is 
well  to  know  how  to  cure  one's  self,  as  well  as  to  aid  others, 
when  need  arises. 

Table  salt  and  vinegar  make  a  good  gargle  for  sore  throat. 
The  vinegar  should  be  diluted  with  water,  if  it  is  unpleasantly 
acid. 

Red  pepper  and  hot  water,  taken  internally,  may  aid  a  cold, 
if  taken  during  its  early  stages.  Drink  a  great  deal  of  water, 
exercise,  and  bathe. 

Mustard  and  hot  water  may  be  used  for  soaking  the  feet 


288          INTRODUCTION  TO  GENERAL  SCIENCE 

in  order  to  cure  a  cold.  Likewise  mustard  plaster,  made  by 
mixing  flour,  mustard,  and  water  and  spreading  the  mass  on 
one  cloth  and  covering  with  another  cloth,  may  be  used  to 
relieve  "  cold  in  the  chest."  In  both  cases,  the  mustard 
acts  as  an  irritant  and,  to  do  good,  must  hurt.  It  causes  the 
blood  to  leave  the  congested  locality,  which  is  all  that  a  simple 
cold  is,  and  thus  produces  relief. 

Cloves  and  allspice,  applied  to  the  gum  near  an  aching 
tooth,  will  relieve  the  pain.  Toothache,  except  neuralgia, 
is  a  warning  to  go  to  a  dentist  as  soon  as  possible.  If  the  pain 
is  neuralgic,  consult  a  doctor;  do  not  use  any  of  the  "  pain- 
killers "  without  medical  advice. 

Baking  soda,  dissolved  in  water  and  taken  internally,  will 
relieve  sour  stomach  temporarily.  Sour  stomach,  if  chronic, 
is  due  to  poor  digestion.  Do  not  chew  gum,  even  "  pepsin 
gum/'  to  cure  indigestion.  It  causes  unnecessary  waste  of 
the  saliva.  Consult  a  doctor. 

Baking  soda,  dissolved  in  water  and  applied  to  the  skin 
before  exposure  to  poison  oak  or  poison  ivy,  will  prevent 
unpleasant  results  due  to  poisoning.  Even  after  exposure,  if 
applied  as  soon  as  possible,  it  may  make  the  poisoning  slight. 
Mere  bathing  will  not  accomplish  any  good;  the  poison  is  an 
acid  and  must  be  neutralized.  In  very  bad  cases  of  exposure, 
just  the  hands  may  be  washed  in  a  solution  of  washing  soda 
and  then  washed  in  clear  water.  Do  not  use  washing  soda 
for  the  face  or  any  part  of  the  body  except  the  hands.  Alcohol 
may  remove  the  poison. 

Cracker  soaked  in  hot  milk  may  be  used  as  a  poultice  for 
local  inflammations  and  swellings.  Do  not  neglect  any 
gathering  of  pus,  as  it  may  lead  to  blood  poisoning. 

Ammonia  should  be  used  to  remove  acids  from  carpets, 
clothes,  or  hands,  and  to  counteract  stings  of  insects. 


SIMPLE  HOUSEHOLD  REMEDIES  289 

Mustard  and  warm  water,  taken  internally,  is  a  good 
emetic,  in  cases  of  poisoning. 

Vinegar  taken  internally  will  counteract  the  action  of 
caustic  potash,  caustic  soda,  or  ammonia. 

Baking  soda,  or  even  the  plaster  from  the  wall,  taken  inter- 
nally, will  stop  the  action  of  all  acids. 

Table  salt  will  prevent  excessive  harm  from  silver  nitrate 
(lunar  caustic). 

White  of  eggs,  milk,  and  gelatinous  drinks  should  be  given 
in  most  cases  of  poisoning,  as  they  tend  to  coat  the  lining  of 
the  stomach,  as  well  as  to  form  insoluble  compounds  with 
many  poisons.  Encourage  vomiting  by  mustard  and  warm 
water.  Send  for  a  doctor  at  once. 

Besides  the  household  materials,  every  home  should  have 
on  hand  a  few  remedies  such  as  corrosive  sublimate,  tincture 
of  iodine,  alcohol,  and  arnica.  All  of  these  are  poisons  if 
taken  internally. 

A  solution  of  corrosive  sublimate,  made  by  dissolving  one 
tablet  in  a  pint  of  water,  is  the  very  best  antiseptic  wash  for 
cuts  or  bruises.  It  kills  any  microorganisms  which  may 
enter,  and  allows  new  tissue  to  be  built  without  loss  of  time. 

Tincture  of  iodine  may  be  used  in  the  place  of  a  mustard 
plaster  and  for  sprains. 

Arnica  and  alcohol  may  be  used  for  sprains  and  lameness, 
and  alcohol  may  be  rubbed  on  the  skin,  after  a  hot  bath,  to 
prevent  a  person  from  catching  cold.  See  Section  11,  First 
Aid  to  the  Burnt. 

References :  — 

1.  1501:148-154.     Drugs  and  Poisons. 

2.  1503:417-418.     Narcotics. 

3.  Farmers'  Bulletin  No.  86.       Thirty  Poisonous  Plants. 

4.  Farmers'  Bulletin  No.  188.     Weeds  Used  in  Medicine. 

D 


290         INTRODUCTION  TO  GENERAL  SCIENCE 

5.  Farmers'  Bulletin  No.  377.     Harmfulness  of  Headache  Mix- 

tures. 

6.  Farmers'  Bulletin  No.  393.     Habit-forming  Agents. 
a.    1505 :  132-135.     Headaches.  —  Drugs. 

6.  1506 :  95-96.  Results  of  Overheating.  —  Alcohol. 

c.  1507:56-61.  Water.  —  Alcohol. 

d.  1507 : 163-164.  Fainting.  —  The  Effect  of  Drugs. 

e.  1509 :  331-335.  Poisons,  Drugs,  and  Chemicals.  —  Anti- 

dotes. 

/.    1509 :  335-342.     Fainting,  Sunstroke,  Drowning,  and  Chok- 
ing. 

g.    1511 : 371-379.     First  Aid  to  the  Injured. 


209.    READING  METERS 

Water,  gas,  and  electric  meters  are  all  read  in  the  same 
manner.  The  dials  are  read  from  left  to  right,  taking  the 
number  which  the  hand,  or  indicator,  has  passed.  If  there 
is  doubt,  read  the  next  dial.  If  this  indicates  8,  9,  or  0,  the 
number  in  the  preceding  dial  has  not  been  passed.  If,  how- 
ever, the  next  dial  reads,  1,  2,  or  3,  the  number  has  been 
passed. 

The  number  over  each  dial  shows  the  total  amount  which 
one  revolution  of  the  hand  in  that  dial  would  indicate.  Thus 
if  the  number  is  10,000,  it  means  that  one  revolution  of.  the 
hand  would  indicate  10,000.  If  the  hand  indicates  6  in  that 
dial,  it  means  6000. 

Gas  is  measured  in  cubic  feet,  water  in  gallons  or  cubic  feet 
(one  cubic  foot  equals  seven  and  one-half  gallons),  and  elec- 
tricity in  kilowatt  hours.  The  unit  of  measurement  does  not 
affect  the  reading.  To  find  the  amount  of  gas,  water,  or 
electricity  which  has  passed  through  the  meter,  subtract  the 
previous  reading  from  the  last  reading. 


ECONOMY  291 

EXPERIMENTS  FOR  THE  HOME 

Leaks  in  the  pipes  or  wires  may  be  made  known  by  reading 
the  meters  carefully  and  then  not  using  any  gas,  water,  or 
electricity  during  the  test.  The  amount  of  water  which  is 
used  on  a  lawn  can  be  measured  and  some  idea  obtained  of 
the  amount  of  water  which  is  necessary  for  keeping  a  lawn  in 
good  condition.  One  gas  burner,  or  one  electric  light,  may 
be  burned,  and  the  cost  per  hour  may  be  reckoned.  It  can 
be  shown  that  a  gas  burner  which  blows  gives  less  light  and 
consumes  more  gas  than  does  a  burner  which  burns  quietly. 
Similarly,  an  electric  lamp  which  burns  dimly  uses  nearly  as 
much  electricity  as  a  lamp  burning  to  full  candle  power. 

References :  — 

1.    1803 : 80.     The  Gas  Meter. 

210.    ECONOMY 

There  is  a  certain  amount  of  waste  in  all  food;  clothing 
cannot  be  made  without  a  loss  of  some  of  the  cloth;  wear  is 
taking  place  in  everything  all  the  time;  heat  is  lost  from 
houses  through  ventilation;  and  there  is  a  constant  tendency 
lor  all  the  material  which  is  available  to  man  to  become  un- 
available. Some  of  the  waste  may  be- prevented  or  dimin- 
ished by  care  and  by  the  application  of  knowledge.  This  is 
economy. 

Sometimes  an  apparent  saving  of  money  is  a  loss  in  the 
end.  When  we  consider  that  all  animal  heat  is  produced 
by  the  slow  combustion  of  food,  we  shall  see  how  erroneous 
is  the  idea  that  a  cheap  barn  is  good  enough  for  stock.  If  the 
horses  and  cattle  are  not  warm,  they  must  eat  more  food  and 
must  change  their  food  into  heat  within  their  systems,  and 


292         INTRODUCTION  TO  GENERAL  SCIENCE 

therefore,  it  costs  the  owner  more  for  food.  Again,  all  food 
which  cattle  use  to  maintain  their  animal  heat,  means  so 
much  less  milk.  Milk  is  produced  after  all  the  other  animal 
needs  are  satisfied;  and  it  might  be  said  in  this  connection 
that  hens,  well  cared  for,  produce  more  eggs  for  the  same 
reason,  viz.  that  eggs  will  not  be  produced  until  all  other 
necessities  of  the  body  are  supplied.  The  wise  farmer  builds 
tight  barns  to  protect  his  stock  from  cold  weather.  He 
reaps  his  reward  in  a  larger  amount  of  products. 

A  few  of  the  household  economies  may  be  mentioned: 
the  use  of  fireless  cookers,  slow  boiling  after  boiling  is  estab- 
lished, home  bleaching  and  dyeing,  recooking  of  food  to  make 
palatable  dishes,  sifting  of  ashes  where  anthracite  coal  is 
used,  the  home  making  of  soap  from  refuse  grease,  the  keep- 
ing of  hens  in  country  places,  which  may  be  fed  for  the  most 
part  with  waste  food,  and  the  use  of  roasts  rather  than  fried 
meats.  Every  housekeeper  could  save  much  in  buying  food 
if  she  made  a  study  of  food  values.  See  Section  191,  Food 
and  Nutrition. 

References :  — 

1:   1503  :  323-325.          Food  Economy  and  Waste.  * 

2.  1702 :  359-361.  Comparative  Cost  and  Value  of  Grains. 

3.  1702  :  382-383.  Economy  in  Food  Values. 

4.  1710 :  308-321.  Economy  in  Food  and  Fuel. 

5.  Farmers'  Bulletin  No.  391.     Economical  Use  of  Meat  in  the 

Home. 

6.  Reprint  from  Yearbook  Department  of  Agriculture  for  1908  : 

The  Wastes  of  the  Farm. 
a.    1701:333.  Dyeing. 

6.    1704:280-281.     Dyeing. 
c,    1712 :  307-314.     Bleaching  and  Dyeing. 


EDUCATION  AND  CIVILIZATION  293 

Experiment  92.  —  Dyeing. 

Apparatus:  Burner,  asbestos  mat,  ring  stand,  two  beakers 
100  c.c.,  test  tubes. 

Materials:  Logwood  solution,  aluminum  sulphate  solution, 
1-20,  ammonium  hydrate  solution,  1-4,  two  pieces  of  white 
cotton  cloth  2"X  2". 

a.  Wash  a  piece  of  the  cotton  cloth  in  several  changes  of 
water,  and  then  boil  it  in  the  logwood  solution  for  five  minutes. 
Remove  the  cloth  and  wash  it.  Result? 

6.  Wash  another  piece  of  cloth  as  before,  dip  it  into  the 
aluminum  sulphate  solution,  wring  and  dip  it  into  the  ammo- 
nium hydrate  solution.  Squeeze  out  the  excess  of  liquid,  and 
boil  the  cloth  for  five  minutes  in  the  logwood  solution.  Try 
washing  out  the  color  with  soap  and  water.  Is  it  "  fast  "? 

The  ammonium  hydrate  and  the  aluminum  sulphate  to- 
gether form  what  is  called  a  mordant.  This  clings  to  the 
cloth  and  also  holds  the  coloring  matter  fast.  Silk  and  wood 
"  take  "  the  dyes  and  do  not  require  mordants.  There  are 
some  dyes  which  do  not  require  mordants,  even  with  cotton. 
These  are  called  direct  dyes. 

211.    EDUCATION  AND  CIVILIZATION 

Education  is  more  than  the  acquisition  of  information.  The 
latter  may  satisfy  our  immediate  want;  the  former  should 
supply  all  of  our  mental  needs.  The  basis  of  education,  how- 
ever, is  information,  but  information  should  be  so  related  to 
what  we  already  know  that  it  will  fit  in  with  it  and  become 
part  of  a  connected  whole.  Otherwise,  the  information  is 
either  lost  or  becomes  part  of  a  jumbled  mass  in  an  unorgan- 
ized brain.  In  order  to  learn  one  thing  well,  it  is  necessary 
that  we  know  a  little  about  a  great  many  things.  We  cannot 


294          INTRODUCTION  TO  GENERAL  SCIENCE 

learn  one  thing  alone,  other  than  a  fact,  for  all  knowledge  is 
one  knowledge. 

The  uncivilized  races  know  how  to  do  a  great  many  things; 
they  know  very  seldom  why  they  do  such  things.  Customs 
and  usages  are  their  masters.  Nature  controls  them,  and 
they  are  helpless  under  unfavorable  conditions  of  weather  or 
health.  There  are  no  connecting  links  to  bind  their  bits  of 
knowledge  together,  and  reasoning  power  has  not  developed. 
Superstition  is  common,  and  their  religion  is  based  upon  sacri- 
fices by  which  the  gods  may  be  propitiated. 

Education  is  the  greatest  civilizing  factor.  It  leads  us  to 
a  fuller  appreciation  of  life  in  its  entirety.  It  destroys  super- 
stitions and  stimulates  ambition  toward  better  living.  While 
there  are  educated  men  who  are  criminals,  education  did  not 
make  them  so,  and  a  more  complete  education,  extending 
back  into  their  parents'  lives,  could  have  prevented  the 
crimes.  When  education  has  advanced  far  enough,  there 
will  be  no  sin,  but  the  education  must  be  general,  unlimited 
by  faith  or  creed,  undimmed  by  prejudice  or  narrowness. 

References :  — 

1.  1501:398.  A  Long  Life. 

2.  1503:11-13.  Science  and  Matter.  —  Classification    of 

Facts. 

a.    1303  :  364-367.    Geographical  Factors  in  the  Life  of  Civil- 
ized People. 

6.    1311 :  346-370.     The  Earth  and  Man. 

c.    1904 : 187.  Educating  the  Public. 


212.    MANNER  OF  LIVING 

The  worth  of  a  man  to  the  world  and  to  himself  is  accord- 
ing to  his  manner  of  living.     One  who  only  works  a  little, 


MANNER  OF  LIVING  295 

eats  a  little,  and  sleeps  a  little  is  not  far  removed  from  the 
animal  state  of  existence.  An  animal  exists,  but,  just  in  so 
far  as  it  shows  intelligence,  it  lives.  Yet  the  life  of  a  man 
holds  possibilities  far  beyond  that  of  any  animal. 

The  difference  between  a  workman  and  an  artisan  is  that 
the  real  artisan  takes  a  pride  in  his  work,  enjoys  it,  and  tries 
to  improve  methods  and  results.  The  workman  performs  his 
labor  as  part  of  the  day's  program,  —  a  necessary  evil,  —  and 
is  no  better  at  the  end  of  a  year  than  at  the  beginning.  There 
are  many  artisans  among  the  so-called  workmen,  and  also 
many  workmen  among  the  self-styled  artisans.  A  man  is 
what  he  does,  irrespective  of  the  world's  classification. 

A  man  who  tries  to  live  up  to  his  possibilities  must  be  a 
producer  —  the  world  must  be  better  for  his  life.  In  order 
to  make  manifest  one's  ability  and  give  opportunity  for 
development  and  productivity,  education  is  necessary.  To 
know  only  how  to  perform  certain  work  produces  workmen; 
to  know  the  reason  why  certain  work  is  performed  in  a  cer- 
tain manner,  as  well  as  knowing  how  to  do  it,  gives  to  the 
world  a  man  who  can  improve  methods,  for  he  understands 
the  advantages  and  disadvantages  of  the  old.  He  becomes 
a  benefactor  —  an  artisan. 

Necessity  has  been  said  to  be  the  mother  of  invention,  but 
educated  laziness  —  a  desire  to  accomplish  something  better 
with  less  unnecessary  drudgery  —  will  do  much  toward  the 
more  civilized  living  of  mankind.  He  who  can  show  the 
method  of  attaining  a  given  end  with  less  work  and  time, 
makes  the  world  a  better  place  in  which  to  live.  He  who  is 
awake  to  the  possibilities  of  life  truly  lives. 


APPENDIX 


APPARATUS    AND    MATERIALS 

These  lists  contain  the  approximate  amount  of  equipment 
which  would  be  required  by  a  class  of.  ten,  with  the  exception  of 
some  pieces  of  apparatus  which  are  to  be  used  only  by  the  teacher. 


APPAEATUS 

10  Alcohol  lamps,  with  collar. 
10  Asbestos  boards,  5"  X  5". 
2  Balances,  Harvard,  with  weights,  500  g. 
1  Ball,  iron,  with  screw  eyes. 
10  Battery  jars,  6"  X  8". 
2  doz.  Beakers,  50  c.c.,  high  with  lip. 
2  doz.  Beakers,  100  c.c.,  high  with  lip. 
1  doz.  Beakers,  150  c.c.,  high  with  lip. 

1  doz.  Beakers,  200  c.c.,  high  with  lip. 

10  Bells,  electric,  3". 

5  Boards,  3'  X  5"  X  7A" ;    narrow  strip  along  edge. 
10  Bottles,  wide  mouth,  500  c.c. 
4  doz.  Bottles,  wide  mouth,  250  c.c. 

1  Brass  tube,  6"  X  1". 
10  Bristol  boards,  22"  X  28". 
10  Bunsen  burners. 
10  Calorimeters,  3"  X  1". 

1  Cannon,  small. 

2  doz.  Cells,  dry. 

10  Chalk  boxes. 
4  doz.  Chimneys,  Argand  or  student. 

1  doz.  Clay  pipes. 

2  Ibs.  Coal,  soft. 

297 


298  APPENDIX 

1  Coil,  induction  J£"  spark. 

5  each  Colored  cards,  red,  bluish  green,  yellow,  blue,  purple. 
10  Copper  rods,  #12,  6". 

1  doz.  Crystallization  dishes,  5". 

2  doz.  Evaporation  dishes,  3". 

1  doz.  Files,  4"  medium. 

2  doz.  Flasks,  250  c.c. 
1  doz.  Funnels,  3". 

4  doz.  Glass  plates,  4"  X  4". 
1  doz.  Glass  tubes,  8"  X  ^". 
1  doz.  Globes,  6". 
%  doz.  Graduates,  100  c.c. 

1  Hammer. 

1  doz.  Holders,  test  tube. 
10  Iron  rods  #12,  6". 

1  Preserve  jar,  1  pint. 

2  Kipp  generators,  1  pint. 

1  Lamp,  electric,  in  socket,  with  cord  and  plug. 
20  Lead  strips,  5"  X  I"  X  Vie"- 
10  Magnets,  bar,  6". 
10  Magnetic  needles,  4". 

1  doz.  Medicine  droppers. 
J^  doz.  Meter  sticks. 

2  doz.  Mirrors,  5"  X  2". 
1  paper  Needles  #5. 

10  Pans,  bread,  12"  X  6"  X  3". 
1  paper  Pins. 

2  doz.  Pith  balls. 
10  pieces  Platinum  wire  #30,  6". 

1  doz.  Porous  cups,  4"  X  2". 

10  Prisms,  60°,  3"  X  V. 
10  Protractors,  4". 

10  Ring  stands,  2"  X  5"  rings  and  clamps. 
1  gr.  Rivets,  brass,  for  paper,  Y^' . 
10  Rubber  rods. 

2  doz.  Rubber  stoppers,  1",  one  hole. 
2  doz.  Rubber  stoppers,  I",  two  holes. 
1  doz.  Rubber  stoppers  to  fit  bottles. 


APPENDIX  299 

50  ft.  Rubber  tubing,  M"- 
1  doz.  Saucers,  enamelled. 

2  pairs  Scissors. 

10  pairs  Screw  eyes,  iron,  one  to  fit  inside  the  other. 

1  Spool  silk  thread,  #00. 
10  Spring  balances,  4/2ooo  g- 

2  Springs,  clock. 

10  Sticks,  30"  X  1"  X  W '. 
20  Sticks,  60"  X  W  X  W. 

1  doz.  Stirring  rods,  8"  X  3/i&". 

10  Supports  for  magnets,  wood. 

10  Syringe  bulbs,  valves  and  tubes  at  both  ends. 

10  Table  tumblers. 

1  gr.  Test  tubes,  6"  X  M". 
Y2  gr.  Test  tubes,  8"  X  1". 

3  doz.'Test  tubes,  8"  X  1",  hard  glass. 

10  Thermometers,  all  glass  (-  10°  to  225°  F.). 
10  Thermometers,  all  glass  (-  20°  to  110°  C.). 

2  doz.  Thistle  tubes,  8". 

5  Thistle  tubes  with  stop  cock. 

4  doz.  U-tubes,  diameter  l",  with  side  tubes. 

1  Vise,  3"  jaws. 
10  Water  traps. 
10  pieces  Window  glass  to  fit  chalk  box. 

2  Ib.  Wire  copper,  #20,  insulated. 

3^*lb.  Wire,  German  silver,  #22,  insulated. 
1  Ib.  Wire,  iron,  #30. 
20  Wood  blocks,  5"  X  2"  X  2". 
10  Wood  blocks,  3"  X  3"  X  1",  with  peg  6"  X  1". 
20  Wood  blocks,  3"  X  2"  X  1". 
10  Wood  blocks,  2"  x  1"  X  1",  slotted. 
10  Wood  blocks,  6"  X  3"  X  1". 


MATERIALS 


1  pt.  Alcohol. 

4  Ib.  Aluminum. 

1  Ib.  Ammonium  chloride. 


300  APPENDIX 

4  Ibs.  Ammonium  hydrate. 

2  Ibs.  Ammonium  nitrate. 

2  Ibs.  Ammonium  sulphide. 
34  Ib.  Asbestos  paper,  thin. 
34  Ib.  Barium  chloride. 

34  Ib.  Barium  sulphate. 
3^  Ib.  Beeswax. 
1  pt.  Benzine. 

H  doz.  sheets  Blotting  paper,  22"  X  28". 
34  Ib.  Bromine. 

]/2  Ib.  Calcium  chloride,  granulated. 
34  Ib.  Camphor. 

3  doz.  Candles,  6"  X  1". 

1  Carbon  dioxide  tank,  5  Ibs. 
1  doz.  sheets  Cardboard,  heavy,  22"  X  28". 
]/2  Ib.  Castile  soap,  powd. 

1  Ib.  Chalk,  powd. 
I  doz.  Charcoal  blocks  for  blow-piping. 

1  Ib.  Charcoal,  wood,  small  pieces. 
34  Ib.  Chloroform. 
1  doz.  pieces  Cigar  box  wood,  6"  X  4". 

5  Ibs.  Clay. 

1/2  doz.  pieces  Cloth,  red,  yellow,  blue. 
1  doz.  pieces  Copper,  6"  X  1A"  X  Ve*"- 
1  doz.  pieces  Copper,  6"  X  1A"  X  Vie"- 
5  Ibs.  Copper  sulphate. 
X  Ib.  Coral. 

4  doz.  Cork  stoppers,  1". 

1  doz.  each  Cork  stoppers,  Argand  size,  top  and  bottom. 
1  doz.  Cork  stoppers  for  porous  cup. 
1  doz.  Cork  stoppers,  flat  and  thin,  1". 
34  Ib.  Cotton,  absorbent. 
1  box  Elastic  bands,  assorted. 

1  Ib.  Ether. 
3/£  Ib.  Ferric  chloride. 

1000  Filter  papers,  5". 

1  pt.  Fish  oil. 
J4  Ib.  Formaldehyde. 


APPENDIX  301 


1  pt.  Gasoline. 
5  Ibs.  Glass  tubing,  34". 

2  qts.  Grape  juice. 

3  Ibs.  Grape  sugar. 
1  oz.  Gun  cotton. 

34  Ib.  Gunpowder. 

4  Ibs.  Hydrochloric  acid. 
1  oz.  Iodine. 

1  piece  Iron  picture  cord. 
3  Ibs.  Iron  turnings. 
1  qt.  Kerosene. 

5  Ibs.  Lead,  in  bulk. 

2  Ibs.  Lead  nitrate. 

3  Ibs.  Lead  carbonate,  basic. 
1  Ib.  Limestone. 

1  qt.  Linseed  oil,  boiled. 

3  Ibs.  Litharge. 

1  doz.  sheets  Litmus  paper,  blue. 
1  doz.  sheets  Litmus  paper,  red. 

2  oz.  Litmus,  cubes. 
3^  Ib.  Logwood,  chips. 
34  Ib.  Magnesium  ribbon. 

5  Ibs.  Manganese  dioxide,  granulated. 

5  Ibs.  Marble,  broken. 

5  Ibs.  Mercury. 

%  Ib.  Mercuric  oxide. 

1  qt.  Molasses. 
3  sq.  ft.  Mosquito  netting. 

1  pt.  Naphtha. 

4  Ibs.  Nitric  acid. 
-   1  pt.  Olive  Oil. 

3^  Ib.  Oxalic  acid. 
2  Ibs.  Paraffin. 

1  oz.  Pepsin. 

1  qt.  Petroleum,  crude. 

1  oz.  Phenolthalein. 
34  Ib.  Phosphorus. 
Y±  Ib.  Pitch. 


302  APPENDIX 

]/2  lb.  Potassium  bromide. 
3  Ibs.  Potassium  chlorate. 
^  lb.  Potassium  iodide. 
1  lb.  Potassium  nitrate. 
3^  lb.  Potassium  permanganate. 

2  Ibs.  Red  lead. 
1  lb.  Rice. 

1  lb.  Rochelle  salts. 
1  lb.  Rosin. 

3  Ibs.  Salt. 
5  Ibs.  Sand. 

]/2  doz.  sheets  Sand  paper,  #  0. 
Y2  lb.  Sawdust. 
1  oz.  Silver  nitrate. 
1  lb.  Sodium  bicarbonate. 
2  Ibs.  Sodium  carbonate,  crystals. 
%  lb.  Sodium  (metallic). 
2  Ibs.  Sodium  hydrate,  solid. 
2  Ibs.  Sodium  peroxide,  in  cubes. 

2  Ibs.  Sodium  sulphate,  crystals. 
1  lb.  Starch,  corn. 

1  lb.  Starch,  potato. 
Y2  lb.  String. 

3  Ibs.  Sugar. 

9  Ibs.  Sulphuric  acid. 
2  Ibs.  Sulphur,  powd. 
2  sheets  Turmeric  paper. 
1  pt.  Turpentine. 
Yz  lb.  Venice  turpentine. 
2  Ibs.  Whiting. 

Yeast. 
1  lb.  Zinc,  granulated. 

10  Zinc  strips,  6"  X  1"  X  1/u". 
2  Ibs.  Zinc  oxide. 


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of  Macmillan  books  on  kindred  subjects 


MACMILLAN'S  COMMERCIAL  SERIES 

EDITED  BY  CHEESMAN  A.  HERRICK 

President  of  Girard  College,  formerly  Director  of  School  of  Commerce,  Philadelphia 
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Each  volume  i2mo,  cloth 

The  Meaning  and  Practice  of  Commercial  Education.  By  the  Editor,  xv  + 
378  pages.  $1.2$  net. 

The  Geography  of  Commerce.  By  SPENCER  TROTTER,  M.D.,  Professor  of 
Biology  and  Geology  in  Swarthmore  College,  Pa.  xxiv  +  410  pages. 
$1.10  net. 

Commercial  Correspondence  and  Postal  Information.  By  CARL  LEWIS  ALT- 
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Comprehensive  Bookkeeping :  A  First  Book.  By  ARTEMAS  M.  BOGLE,  Head 
of  Department  of  Mathematics,  High  School,  Kansas  City,  Kansas,  xi  + 
142  pages.  90  cents  net. 

Bookkeeping  Blanks.  By  ARTEMAS  M.  BOGLE,  Four  numbers.  75  cents  a 
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Teacher's  Manual  to  Accompany  Comprehensive  Bookkeeping.  By  ARTEMAS 
M.  BOGLE,  vi  +  75  pages.  $1.00  net. 

Elements  of  Business  Arithmetic.  By  ANSON  H.  BIGELOW,  Superintendent  of 
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The  Idea  of  the  Series 

This  series  is  prepared  in  the  belief  that  disciplinary  education  can  be  secured 
through  the  use  of  subject-matter  of  practical  worth.  Much  that  is  fixed  in  our 
system  of  education  is  retained  and  given  new  application;  new  elements  are  in- 
troduced and  are  properly  related  to  the  old.  In  brief,  the  plan  is  to  modernize 
the  instruments  of  instruction  and  make  schools  more  effective  as  a  preparation 
for  present  economic  life.  The  best  from  foreign  books  has  been  utilized  for 
suggestion;  the  best  in  our  educational  development  is  preserved.  The  plan 
and  its  execution  are  the  work  of  experienced  teachers.  The  books  are  products 
of  specialists,  working  under  the  general  supervision  of  the  editor.  Each  volume 
is  adequate  to  its  subject,  authoritative,  and  supplied  with  a  working  equipment 
such  as  illustrations,  maps,  and  diagrams. 


Elements  of  Business  Arithmetic 

By  ANSON  H.  BIGELOW,  Superintendent  of  Schools,  Lead,  S.D.,  and 
WILLIAM  A.  ARNOLD,  Director  of  Business  Training,  Woodbine  (Iowa) 
Normal  School.  Cloth,  izmo.  xv  +  254  pages. 

The  preparation  of  this  text  was  undertaken  in  the  belief  that  the  arithmetic 
of  the  grammar  school  and  of  the  commercial  course  of  the  high  school  should 
teach  tlie  methods  most  in  vogue  in  the  business  world,  and  that  those  methods 
should  be  so  taught  as  to  form  correct  habits  in  those  who  are  to  attack  the  prob- 
lems of  real  life.  It  is  distinctly  a  business  arithmetic,  presenting  the  minimum 
of  theory  and  the  maximum  of  practice  in  business  methods.  Various  methods 
are  presented,  but  only  those  used  in  practical  business  computations.  The  topics 
treated,  by  chapters,  are:  addition  and  subtraction,  multiplication  and  division, 
decimals,  fractional  parts  (short  methods),  fractions,  measures  (length,  are,a,  vol- 
ume, time,  weight,  and  value),  French  metrical  system,  percentage,  trade  dis- 
count, commission,  taxes  and  duties,  interest,  banking  and  discount,  stocks  and 
bonds,  insurance,  proportion,  proportional  parts,  and  partnership.  These  subjects 
are  chosen  with  reference  to  business  needs  and  they  are  treated  in  such  a  man- 
ner as  to  give  the  pupil  the  largest  possible  amount  of  drill  in  practical  business 
methods.  The  book  purposely  brings  the  work  of  the  school  and  the  needs  of 
common  life  into  vital  connection.  It  is  suitable  for  use  in  the  grammar  school 
and  in  the  commercial  courses  of  the  high  school. 


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The  Meaning  and  Practice 
of  Commercial  Information 

BY  CHEESMAN  A.  HERRICK 

The  book  above  mentioned  explains  the  idea  and  describes  the  actual  word- 
ings of  commercial  schools.  It  treats  commercial  education  from  various  points 
of  view,  and  shows  that  this  form  of  instruction  is  a  result  of  present  economic 
conditions  and  a  natural  step  in  our  educational  development.  The  author  shows 
also  that  special  education  for  the  present  commercial  age  is  both  possible  and 
desirable,  and  that  such  education  will  gradually  bring  about  a  higher  form  of 
commercialism. 

The  work  reviews  the  movements  to  furnish  commercial  education  in  leading 
countries.  For  the  United  States  a  series  of  chapters  are  devoted  to  the  Private 
Commercial  School,  the  High  School  of  Commerce,  the  Curriculum  of  the  Sec- 
ondary Commercial  School,  and  the  Higher  School  of  Commerce.  Numerous 
illustrations  of  men  and  institutions  are  furnished. 

An  appendix  supplies  a  good  number  of  curricula  for  schools  of  various  grades. 
The  value  of  the  work  is  further  increased  by  a  select  bibliography  of  the  subject. 

The  Geography  of  Commerce 

BY  SPENCER  TROTTER,  M.D. 

This  book  is  exceptionally  fortunate  as  well  as  unique  in  its  authorship.  Dr. 
Trotter  is  a  scientist  and  geographer  of  high  standing,  while  the  editor,  Dr.  Her- 
rick,  is  a  trained  economist.  Both  are  experienced  and  successful  teachers.  The 
text  has  stood  the  test  of  work  with  high  school  students. 

The  Geography  of  Commerce  gives  a  clear  presentation  of  existing  conditions 
of  trade.  Throughout  the  book  emphasis  is  laid  on  the  relation  between  physi- 
ography, climate,  etc.,  and  the  activities  and  the  organizations  of  men.  As  a  re- 
sult, the  book  is  on  the  "  practical  side  "  of  geography.  Trade  relations  between 
the  United  States  and  other  countries  are  given  special  prominence.  The  causal 
relations  of  physical  environment  to  men,  of  men  and  environments  to  products, 
and  of  products  to  trade,  are  treated  with  a  unity  that  makes  the  book  admirably 
suited  to  class  use. 

A  complete  working  equipment  and  a  list  of  books  for  further  consultation 
are  furnished.  Supplementary  questions  and  topics  are  also  supplied. 


PUBLISHED    BY 

THE   MACMILLAN  COMPANY 

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Commercial  Correspondence  and 
Postal  Information 

BY  CARL  LEWIS  ALTMAIER 

Mr.  Altmaier's  work  supplies  two  present  needs,  a  text-book  for  school  use 
and  a  handbook  for  office  use.  In  the  first  place,  his  book  is  a  working  manual 
for  instruction  and  practice  in  letter  writing,  and  thus  it  furnishes  material  for 
practical  English  composition.  Correct  forms  of  letters  are  furnished,  after  which 
the  learner  is  asked  to  deal  with  situations  of  the  kind  actually  met  with  in  busi- 
ness correspondence.  The  treatment  of  correspondence  is  supplemented  by  a 
somewhat  detailed  accoiint  of  postal  arrangements,  both  domestic  and  interna- 
tional. The  book  is  illustrated  with  photographs  of  documents,  reproductions  of 
actual  letters,  and  a  postal  map  of  the  world. 

Comprehensive  Bookkeeping 

BY  ARTEMAS  M.  BOGLE 

A  few  of  the  points  that  commend  this  volume  are : 

I.  The  gradual  and  systematic  development  of  the  subject.  2.  Preliminary 
sets  for  drill  followed  immediately  by  more  concrete  sets  for  the  more  advanced 
work  of  the  student.  3.  Material  so  arranged  that  the  teacher  may  use  it  largely 
in  his  own  way.  4.  The  sets  so  arranged  that  short  exercises  or  longer  ones  may 
be  given  as  may  be  most  advantageous.  5.  Provision  for  drill  on  important 
points  and  at  the  place  where  needed,  thus  insuring  the  mastery  of  each  point. 
6.  Arrangement  such  that  at  almost  any  stage  previous  points  may  be  reviewed 
without  going  back  and  working  over  the  old  material.  7.  Clear,  concise  expla- 
nations. 8.  A  large  number  of  cross  references,  showing  the  connection  of  one 
portion  of  the  subject  with  another. 

4 

Teacher's  Manual  to  Accompany  Comprehensive 
Bookkeeping 

BY  ARTEMAS  M.  BOGLE 

This  book  contains  the  results  of  computations  required  by  the  regular  series 
of  exercises  given  in  Bogle's  "  Comprehensive  Bookkeeping."  These  tables,  giv- 
ing the  "  answers  "  which  should  be  right,  save  the  teacher  labor  in  checking  up 
pupils'  results.  The  forms  are  not  intended  for  models  but  only  as  results  to  save 
labor  by  the  teacher. 


PUBLISHED    BY 

THE  MACMILLAN  COMPANY 

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UNIVERSITY   OF   CALIFORNIA  LIBRARY 

THIS  EOOK  IS  PI7E  ON  THE  LAST  DATE 
STAMPED  BELOW 


AUG  d 


MAY  121917 

JUl  -9  19.7 

MAY  27 1918 


FEB  10    1932 


JUL  ft 


YR  5930! 


32 


UNIVERSITY  OF  CALIFORNIA  UBRARY 


